First off, the major difference between Guild Wars and MMORPG's is the servers. You are technically in a large graphical chat room in Guild Wars, and all combat is handled with instances. It's a much simpler way of handling a multiplayer game, and hence the server and admin costs are kept to a minimum. It is much more similiar to Diablo than WoW.
Secondly, monthly costs for MMORPG's have been explained ad nauseum on these boards. If you still don't get the economic model behind it, then you are just looking for reasons to dislike these types of games. Also, WoW has yet to release a single expansion. They have over 100 servers running with admin teams, GM's, and testers, as well as programmers and artists churning out new content every month. They would either be broke, or not be able to offer this support, without a monthly fee.
Now Everquest 2, on the other hand, does seem to milk its customers. But then again, the content they release is for the nutcases that play 10 hours a day, so the cost per hour is probably pretty good for the gamer.