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.
More than a bit.
Simply give people the option to put a charge limit and let the app be offline when that limit gets hit. Don't make it the default, but do allow people to do it.
This would resolve 99% of the fear people have. And most people wouldn't set the limit anyway. However, your knowledgable people might set it, and those are the ones you're most trying to attract.