> But it would be “cheap” once established because cooling would be easy.

I would imagine that if you put a datacenter in orbit or on the moon (or pretty much anywhere else in space), cooling would actually be significantly more difficult, if for no other reason than that in a vacuum the only way of getting rid of heat is via radiation. On earth, you can at least dump the heat out (much more efficiently) via convection into the atmosphere or conduction into a large body of water, or something similar.