1) You don't "upgrade" to IPv6, you offer it inline with IPv4. It has never been a forklift replacement (there is another rule about this).
2) I have worked for numerous ISPs over the years, big and small. Way more than three I can tell you, and the small ones are almost always the ones pushing IPv6 hardest, because CGNAT is fucking expensive. The big ISPs are the ones who are ignoring it. I've only worked for one small ISP that was opposed to it, and their attitude changed when they ran out of IPv4 space, and saw their choices. CGNAT or buy more space on the open market.
So I hear you on that side, not everyone can get native IPv6. That is a true issue.
But holy hell, the number of networks I have worked at where we pushed IPv6 without incident damn near everywhere. And then I'd get a call escalated to me from some IT "pro" demanding I remove IPv6 support from his service because it wasn't ready for production use and how dare I enable for it our customers.
I had working native IPv6 on TWC in 2016 when I ordered the service. When Spectrum bought TWC, they actually ripped out IPv6 support. I didn't get it back until last year.
The dumbassery is everywhere, and none of it is IPv6s fault. It's shitastic people.
Oh, and I just caught that claim about IPv6 being pricey.
BULL FUCKING SHIT. Pure and utter nonsense.