[barsky]

I remember Maciej saying he collocates his servers, which works out to be remarkably cheap in the long run. I'd assume the server costs are actually pretty small, relative to the income of the site.

[idlewords]

Those costs are public. See https://docs.google.com/spreadsheet/ccc?key=0Au7yiR802qQmdDJ...

The link is for 2012, but they haven't changed much.