>The top servers are paying tens of thousands a month in hosting.

Are you just speculating? This seems extremely high. I've hosted a couple Minecraft servers and even with a mild constant population (~30) it wasn't even breaking 100/mo.

>DDOS protection is pretty much essential to any server over a certain size, which increases costs significantly.

I've had many dedicated servers in my day, and this has never been the case. Not sure where you're getting this data from.