All of the home ISPs I've used in the past 10 years have IPv6. I know a few don't, including some surprising ones such as new FTTH, but they all say it's "coming."
Once you wire fiber upstream bandwidth doesn't matter that much. ISPs are directly peered into the core of the Internet and pay bulk peering bandwidth pricing not cloud bandwidth pricing. Cloud bandwidth pricing is completely insane, like 10000% markup or more in many cases, and the fact that they charge more for outbound is just a strategy to make data flow into their cloud but not out. Bandwidth is actually dirt cheap or companies like Cloudflare could never exist.
The main reason they drag their feet on IPv6 is that there's no strong forcing function and dual stack adds complexity. When they're on a deadline to ship they punt on it. They are starting to get complaints from gamers though. Gamers tend to be the top home users that drive early adoption of all kinds of things.
Edit: another funny thing is that most ISP/telecom stuff these days is IPv6 at the core. If they're not doing it at the edge for new stuff it means they've just got it off and are running IPv4 over IPv6 within their network most of the time. This is even more true for mobile networks, some of which are IPv6 only and the phone does 4to6.
The rollout is still happening... slloooooooowly... The Internet is huge and it takes forever to do a major upgrade like this. I wish they'd have just made IP 48 or 64 bit with an easier upgrade path, but that's water under the bridge now.