Playing is free at many sites and that is enough for plenty of people; they play and don't pay and yeah verily, it is good. So I rather think it's actually the extras that earn the money. Some sites won't give ratings to non-paying members and people will pay to have and work towards a good rating. Some sites provide customisation and ease of use factors which people who play a lot will pay for. At Vogclub, people pay to have a permanent membership account instead of having to re-register a new name every few weeks and/or for the ability to save matches to disk (not possible here yet), and to access the searchable archives (available on a limited basis here). Here, people pay to be able to have more than 20 games going at once, for the ability to have teams and fellowships and cloaks, javascript(?) and what-have-you (I don't know too much about those things yet).