Last verified: 2026-09-18 · Locked hub formulas only · planning only · not a payout
Seller fee calculator methodology — locked KEEP math & sources
How RealRateCalc builds citeable seller-fee numbers. Every cell on the fee index and every /fees/{platform}.json feed mirrors a locked KEEP hub — no invented rates.
1) Source policy (lock file concepts)
A fee is shippable only when it meets all of:
Official source URL — the platform’s own help / pricing / legal page (linked on the KEEP hub as “Official source”).
Locked starting formula — the same math that paints hub #out on a $100 sale with shipping/plan at $0.
Hub twin — a live /{platform}-keep/ page you can open to re-run the inputs.
No invented fees — category-unclear, size/weight, or promo-only lines stay presets or PARKED, never first-paint.
Per-platform feeds list those official URLs + the same-input $100 KEEP from the fee-index lock.
2) First-paint rules
First-paint KEEP = what you see when the page loads (defaults). On hubs that is typically sale $100, shipping $0, monthly/plan $0.
Fee-index rows and /fees/*.jsonkeep_on_100 copy that first-paint number — e.g. Shopify Basic $96.80 · Depop $96.25 · Etsy $90.05 · eBay $86.00 · Poshmark $80.00.
Extra price points ($10–$250) apply the same locked formula; they are not new rates.
QA on compare uses hub first-paint as the ground truth ($100 KEEP mismatch → fail).
3) Leftover / ads toggle rules (D2-W lock)
Optional only: Etsy Offsite Ads (attributed) and eBay Promoted Listings General (CPS).
Default OFF — never included in first-paint KEEP on hubs, fee-index, or JSON feeds.
When toggled ON (compare / etsy-vs-ebay), the cost shows as a separate purple Ads leftover layer — labeled not marketplace take.
Caps and rates follow the official help pages cited on those tools; toggles are stress-tests, not the locked starting keep.
4) Planning-only honesty
Numbers are educational planning math, not a payout, remittance, or tax advice.
Confirm on the linked official docs before you list — Store plans, categories, shipping basis, tax, and promos can change net.
Not affiliated with the marketplaces listed (Shopify Impact bridges, when present elsewhere, are disclosed with exact FTC language).
Dated deltas live on /fee-changes/ — copied from hub official sources only.
Only locked official starting formulas from each KEEP hub (#out first-paint on $100), cited to the platform’s own help/pricing/legal page. Fee-index cells and /fees/{platform}.json copy those locks — no invented fees.
What is first-paint KEEP?
The number shown when a KEEP hub or compare table loads with default inputs (typically $100 sale, $0 shipping/plan). Optional ads leftovers are OFF and never change first-paint.
What are ads leftovers?
Optional Etsy Offsite Ads and eBay Promoted Listings General costs on compare / etsy-vs-ebay. Toggles default OFF. When ON they appear as a separate ads leftover layer — not marketplace take (D2-W lock).
Is this a payout guarantee?
No. Planning only. Confirm on the linked official docs before you list. Category, Store, shipping, tax, and promo lines can change what you actually receive.