I hate services that don't put a price on things like bandwidth (because there's always a price!). So we priced bandwidth and made it transparent. You can put an app on Fly.io and server petabytes of data every month, if you want. We'll never complain that you're serving the wrong content type.
But the reality is – having an unlimited bandwidth promise is perfect for for a fire and forget blog site. We're not doing ourselves any favors with scary pricing for that kind of app.
A feature that could help would be giving people the option to set a cost limit, where if their site surpasses that limit in a given month you just pull it offline instead of charging more money. That's what I'd want for my blog site, and I've heard others request such a feature from other cloud providers