Some people are more UoA maximalists and pick a bitcoin price (e.g., 10m sats) and stick with it. Probably not sustainable since it makes their products more and more expensive in USD terms over time.

What's worse, I've found, is what happens when the transaction isn't spot: say I do some work for a client beginning on Jan 1, when BTC/USD = 100k. Then I finish the work and ask for payment on Jan 30, when BTC/USD = 120k. At which rate (USD or sats) does the dude pay me?

Worse still: I did a job for a guy a few years ago where he'd pay me half by finish and half by end of year. When he paid me first, BTC was ~40k. When he paid me second it was like 20k or something.

These sort of merchant-customer, client-employer relations get weird.