Seriously, bandwidth just is SUPER cheap period. The fact that some people theoretically might not even have $4.99 to kick towards their "hobby" does not negate that fact.
Like I said above, I did all the stuff I did with nothing more than $5/$10 month cloud hosting plans. Almost no one is going to hit any kind of bandwidth limits these days unless they are trying to run SaaS or just pirating full BluRays in the dumbest ways possible. But we're not talking about those people, we're talking about hobbyist content creators.
i'm a hobbyist, I've been slashdotted, front page of hn multiple times, and on other high profile sites that sent _lots_ of traffic. bandwidth cost is simply not an issue unless you're self hosting video files or some other obscenely large files, and there's no reason to be self hosting things like that. It would only be a concern if a botnet started hitting me with requests. I'm not on any fancy server plan.
That being said, I do pay for a monthly plan, because relying on free handouts for anything that matters is never a reasonable approach.
Simply being sensible about what kind of files you're asking people to download solves 99.9% of this problem and makes your site more enjoyable (faster) for users (especially mobile ones).
a) you're a hobbyist/minor (effective budget of $0)
b) you're on cloud hosting and go over without a budget set