Some years ago at an IETF one of the talks was about an outfit whose hosting or cloud or something pricing change was designed to prod people towards IPv6. Something like, on contract renewal you could keep the same config, same price, for the next period, but you only get IPv6, or, you could decide you must have IPv4 still, but that's a separate product now, so you need to get your finance people to sign off on the revised billing with the small extra cost for the v4 addresses you'll need as they're no longer baked in. One reason to do this was because v4 addressing does actually cost money, but they also expected it would itself drive migrations to IPv6 and they were correct.
Because "We should fix our thing to work with IPv6" sounds potentially like a fun learning experience whereas "We should talk to our finance department" sounds miserable so they're obviously gonna put a few hours into making IPv6 work rather than take the "easy" option.
IIRC They did have customers who paid for IPv4 after the changes, but the vast majority went IPv6 only.
