Fair point. I used 1% at the very low end -- if the amount is small enough (in the $1/month range) I think the opt-in rate would be much higher.

I would then give a free account to anyone who asks. ("We know that even $1/month is a big ask for some folks in certain countries or they may even have a method by which to pay it. If that's you, let us know and apply for a free account here.") Then basically auto-approve (with some bot-screening mechanism) accounts that apply. Sure you'll get some abuse and people lying, but not that many people are going to lie just to save $1/month.

Does that even matter if the mission is dead?

that's one percent more success at the mission than you have if you're forced to turn the servers off because you can't pay the bills. Money's to an organization what's oxygen is to a body, before you go and plan any missions you need to be able to sustain yourself.

Another alternative is charging $10/month, but allowing students or anyone to request a waiving of fees. They just need to take a minimal speed-bump action to request it, e.g., sending an email once per year. Anyone who isn't willing to do this probably isn't getting much value anyway, and a non-trivial fraction of people (more than 1%) would plausibly pay $10/year just to avoid the speed bump or to support the mission.