SellerKit
As described:StopNarrowed:NarrowNo as described. Go, small, as a KDP backlist pricing and promotions extension.
self-publishing · ~$20 a month per paying account · last reviewed (next review by 29 Dec 2026) · 29 cited sources
Start this week
- Tell me your hours per week available, whether you publish on KDP yourself (and how many titles), and whether you've shipped a Chrome extension before.
- Log into KDP and confirm there is no bulk price or rights update anywhere in the Bookshelf (one search summary claimed there is; the help pages say otherwise). If one exists, stop and tell me.
- List 40 publishers with 20+ titles you can reach (author groups, Kboards, newsletters), and book 15 calls. Ask how they handled the July 2026 royalty change and their last price promotion.
- Build the manual kit: a spreadsheet of titles × formats × marketplaces × current price × royalty option, and a one-page "stuck at 35%" check you can run for someone on a screen-share.
Checkpoints and kill gates
Decide in advance what counts as on track. Missing a checkpoint means changing the buyer or the offer, not adding features.
Day 30
~15 hrs/week
15 publisher calls, 6 paid done-for-you reprices
Full-time
20 calls, 10 paid reprices
If you miss it
Switch the buyer once, to small presses and multi-pen-name publishers only. Missing twice means stop.
Day 90
~15 hrs/week
Extension listed, 20 paying accounts, ≥60% renew after month 1
Full-time
Listed, 40 paying, ≥60% renew
If you miss it
Cut to the single most-used flow (usually bulk repricing), and push annual plans.
Month 6
~15 hrs/week
$600 MRR, ≥25% of payers used the promo scheduler
Full-time
$1k MRR, same usage
If you miss it
Pivot A: cross-store promo pricing for "wide" authors. Pivot B: annual-only "backlist audit" plan.
Month 12
~15 hrs/week
$1.5k MRR, monthly churn ≤5%, zero unresolved breakages over 48 hours
Full-time
$3k MRR, churn ≤5%
If you miss it
Stop adding features. Fix churn and onboarding. A profitable $1.5–3k is a valid outcome.
Month 18
~15 hrs/week
$2.5k MRR
Full-time
$4.5k MRR
If you miss it
Put everything into the best channel. Decide on the second store.
Month 24
~15 hrs/week
$3.5k MRR
Full-time
$6k MRR
If you miss it
Above target with churn ≤5%: aim for the $10k rung in year 3. $1k–target: run it profitably, or list it for sale (Merch Wizard sold in 5 hours). Below $1k: stop.
Do
1.Make KDP backlist pricing the product. One job: "change prices and royalty options across all my books and formats, in one pass, with a preview and an undo."
Target: Every listing line says "bulk pricing for KDP"
Why: KDP's help pages describe price changes one title at a time (ebook: Edit eBook Pricing; print: Edit rights & pricing). No bulk or scheduled option is documented.
2.Launch into the July 2026 royalty change. The 70% ebook band rose from $2.99–9.99 to $2.99–12.99 on 7 July 2026. It's opt-in, title by title. Ship a free "find my books stuck at 35%" check first.
Target: 500 free checks run by day 90
Why: Every author with titles at $10–12.99 has a reason to act now. It's the Merch Wizard playbook: a free tool builds the list.
3.Add the timed promo scheduler as the recurring job. Set a promo price for chosen titles, marketplaces and dates. The extension applies it and reverts it when the author next opens KDP, with a reminder.
Target: ≥50% of Pro accounts schedule a promo each month
Why: Kindle Countdown Deals are limited to KDP Select titles and a few marketplaces. Everyone else changes prices by hand, twice per promo. This is the monthly habit that fights churn.
4.Add a backlist health check: books below the print price floor after cost changes, 35% titles that qualify for 70%, prices out of line across marketplaces, missing series links, empty keyword slots.
Target: A monthly email report to every account
Why: It's the reason to open the extension when nothing else is happening, and the source of the next repricing job.
5.Keep the user in control on every write. Batches run only when the user clicks, in their own logged-in tab, at human pace, with a preview first and a log after. Never log in for the user, never run headless, and never run on a server.
Target: Zero server-side access to any KDP account
Why: KDP's terms have no bot clause, but Amazon can terminate "if we have concerns". Amazon's March 2026 Agent Policy bans browser automation on Seller Central. A tool that looks like a bot is one policy update from being banned.
6.Price it by catalogue size, subscription only: Author $15/mo (up to 40 titles), Pro $29/mo (up to 200), Press $69/mo (unlimited titles, several accounts). Annual at 10× monthly. A free tier covers the health check and up to 5 titles.
Target: Blended ≥$20. ≥40% of payers on annual by month 12.
Why: Merch Wizard charged $9.99–14.99 in 2019, and Rick Blyth's $12.99 one-time extension made only $3k. Book Report charges authors $19–249/mo for reporting, by earnings. Prolific publishers pay.
7.Sell before you build: a done-for-you backlist reprice for a fee, using a spreadsheet plus your own hands in a screen-share.
Target: 10 paid by day 30
Why: It proves the pain and teaches you every KDP pricing edge case (marketplaces, formats, KDP Select, list-price rules) before you write code.
8.Automate breakage detection from day one. The extension checks its selectors every time it loads and reports failures anonymously. Keep your own KDP test account with draft titles, and run the full flow on it after any alert.
Target: Breakages detected within 1 hour, fixed within 24
Why: Page changes are the #1 way extensions die. Customers forgive a fix in hours. They cancel after a week of silence.
9.Go where prolific authors already gather: author Facebook groups, Kboards, author YouTube channels and newsletters, with live demos and an affiliate offer (30% recurring).
Target: ≥50% of new payers from communities and affiliates
Why: That's exactly how Merch Wizard grew: Facebook groups, influencer affiliates, live demos, Chrome Web Store search. No paid ads.
10.Own the search terms around the change: "KDP 70% royalty $12.99", "change KDP price all books", "KDP price promotion without Countdown", "bulk edit KDP".
Target: 10 guides by month 4, ranked on page 1 for 3 of them
Why: Authors search by the exact problem. The July 2026 change is a fresh query with few answers.
11.Store almost nothing. Price plans and logs stay in the browser (chrome.storage). The server holds only the license. Say so on the listing.
Target: Privacy disclosure lists "no book data leaves your browser"
Why: It passes Chrome's limited-use policy, it reassures authors wary of Amazon bans, and it keeps you out of data-protection work.
12.Plan the exit valve: cross-store pricing. If paying users ask, add Kobo Writing Life, Apple Books and Google Play Books, so one promo applies everywhere.
Target: Decide at month 9, only if ≥30% of payers publish "wide"
Why: Amazon has no reason to build pricing sync with its competitors. It's the one feature Amazon won't ship for free.
Avoid
1.A generic "seller dashboard" extension across several platforms
Why: Each dashboard is its own product, with its own DOM, terms and community. Six half-products break six ways.
2.Amazon Seller Central
Why: Amazon's Business Solutions Agreement Agent Policy (4 Mar 2026) allows automation only through the SP-API, and names browser automation and screen scraping as prohibited (secondary sources). Helium 10 and Jungle Scout already own the category.
3.Amazon Merch on Demand
Why: At least 8 upload and research extensions are live (MerchAuto, Merch Titans, MerchGhost, Merch Dominator, Snap, Merch Image Uploader, free MerchSpark and Productor). The category is saturated, the upload tools sell "bot safety", and accounts get terminated.
4.Etsy
Why: Etsy's API terms bar browser extensions from accessing or scraping Etsy without written permission (search summary; the page blocked the fetch). Bulk edit is already sold through the official API (Vela from $10/shop/month, Evlista, Sale Samurai). EverBee has 200k extension users for research.
5.Meesho and Flipkart seller panels as the first market
Why: The pain is real (returns, lost-order claims), but extensions already sell there for ₹29/month. Customer numbers would have to be about 40 times higher for the same MRR.
6.Bulk uploading new titles
Why: KDP Uploader (2,000 users) and others already do it. It also serves mass low-content publishing, which Amazon restricts, and it looks most like a bot.
7.KDP sales analytics as the product
Why: KDP's own dashboard has improved. Book Report ($19–249/mo) and Publisher Champ ("25,000 authors", $16.99–29.99/mo) own reporting.
8.Background automation: running while the user is away, auto-login, headless browsers, servers holding KDP sessions
Why: It's what Amazon's Agent Policy bans on Seller Central, and it's what gets accounts terminated. One banned customer account in an author group ends the product.
9.Scraping Amazon product pages (competitor prices, BSR, keyword research)
Why: Amazon's site conditions forbid data mining and robots (not re-verified this run). It also turns a pricing tool into a research tool, a crowded category (Publisher Rocket, KDSpy, Book Bolt).
10.One-time pricing or lifetime deals
Why: Rick Blyth's $12.99 one-time extension made $3k in total. His subscriptions made $10k a month. Lifetime deals pay once for maintenance that never ends.
11.A Firefox or Safari version before $3k MRR
Why: Every browser is another codebase to keep in step with KDP. Chrome and Edge share one build.
12.Remote code or remote selector scripts
Why: Chrome's MV3 rules require all logic to ship in the reviewed package. A shortcut here gets the listing pulled. Ship selector fixes as normal updates.
13.Paid ads before month 6
Why: The buyer pool is small and lives in communities. Ads to "authors" are broad and expensive.
14.Adding features when a checkpoint fails
Why: A miss means the wrong buyer or the wrong job. Change that, not the feature count.