My correction is for static prefixes from an ISPs block, I don't see that as an unreasonable free request. No peering, they just static route that block to the IPv6 address they assign you.
But in the general case, for a customer who is just using the Internet from the same place as last time, there's no benefit to changing their IP addresses and clearly there's no reason static addressing shouldn't be free, it's just like one database entry for them to do it.
I could imagine them explaining OK, you get static BUT it might change if you move home or something, and that feels pretty acceptable to me.
For what it's worth I get static IPv6 and IPv4 (although of course the IPv4 is a tiny block, only a /27 IIRC whereas I have a /48 of IPv6) but I'm in the UK and with a specialist ISP that cares a lot about this stuff.
Even some of the large ISPs can get it right. I used to have fiber optic service from a large telephone company (starts with "C" ends in "EnturyLink") and could use their account management portal to go and get anything up to a /26, complete with setting up reverse DNS, just by clicking a button and agreeing to a relative pittance of money. I think the /26 was $40 per month and the /28 I had was $10 a couple of years ago. They would give me a static IPv6 /48 for nothing, just a click, and delegate the reverse DNS zone to me. A /56 that was supposedly dynamic but never actually changed was given by default.
The problem seems to be which ISPs want to do what. ISPs run by phone companies seem to think of their networks, and the customer networks attached to them, as actual internetworked networks. ISPs run by video companies seem to think of their networks as extensions of distribution systems for linear television channels.