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.
Things like alerts are fine, professionally, but not for things like running a small app, blog or whatever, that you’re not sure where is heading.
I don’t think anything I’ve build on my own time has ever ended up breaking my bank, but signing up my credit card is a risk I’m never going to take, and I’m fairly certain I’m not alone in that. Of course I have no idea if there are enough of us to make small scale fixed prices products profitable at scale.
With Heroku it is stupidly simple to get things going, no credit cards, "fire and forget". Works great for hobby projects, and examples you want to show.