Reddit should realistically charge for lost revenue rather than lost expenses. Instagram makes $50B annual revenue on 2 billion users, or around $25/user/year. I'm certain that Reddit is making nowhere near that per user, but they're probably pricing their API along their most optimistic projections.

I don’t really think of any number, because that would be silly. None of us know the answer nor can we confidently estimate what it is. Therefore any attempt to justify or argue costs by us is useless.

No. It’s made up, because whether you claim it’s 20x or 100x or -5x, you can’t defend any of those numbers because of incomplete info.