I'm on an incredibly small instance that self reports costs at about $18 USD/month, which is above your costs.
Beehaw reports costs at over $500 USD/month.
I would imagine lemmy.world is in the thousands.
I know the idea is that there should be more instances, but we are already beginning to see server costs that are higher than what you think. User numbers seem to be settling down now, but who knows when the next spike will happen.