Both bots I run are just for ephemeral responses, so unfortunately I'm not sure. I tend to be well under the $5 threshold, though, even at 2x bots, so it seems like there's plenty of wiggle room for more storage without incurring totally nutso costs.

(And even if you do exceed the $5 threshold, it's still waaaaaay cheaper than other options I've seen. RIP to Heroku's free hobby tier.)