• After you pay, it’s their money. You don’t have a right to know or control whether they hold or sell unless that was agreed before the payment.
• If it matters to you, make it part of the deal up front. Ask for a “we keep X% in BTC” policy in exchange for a small discount. No agreement, no expectation.
• Vote with your spend. Pay BTC to merchants who publicly keep some BTC or use non-custodial rails. Pay fiat to everyone else. No shaming, just selection.
• Decide case by case with a simple check:
  Value you get
  • how much it matters to you to support BTC use
    − exchange fees/traceability you don’t like
    − hassle to pay in BTC
    If that total feels positive, pay in BTC. If not, pay fiat.
• Merchants who instantly sell aren’t “wrong.” Many have fiat bills, thin margins, and tax constraints. A circular economy grows faster when more people can earn and settle costs in BTC, not by policing what happens after a sale.
• Practical options (only if both sides want them):
  • Two prices: fiat price and a BTC price that improves if the merchant keeps more BTC.
  • Simple proof: the merchant states a retention band (e.g., 20–50%) or shows they run non-custodial Lightning. If they don’t, the price reverts to the standard rate.
  • “Minimize exchange use” pledge: merchant prefers P2P or non-custodial rails. If not, they lose the BTC price perk.

Bottom line

• No right to control post-payment. If retention matters, price it into the deal or choose a different merchant. Build the loop with contracts and choices, not with moral pressure.