I actually had this very same discussion with a friend of mine. He too said that he would rather buy a game and NOT have to pay for it everymonth thereafter. Wouldn't we all? The thing is though, say I play WoW for a year, that's £30 one off for the game, and then £9 a month for 11 months (1 month free trial) that's £129 for a year of entertainment We then compared that to how much he'd spend on games throughout the year. Say he buys one, just one, game every month for the year that I play WoW and say that each game costs him, on average, £30. 30 * 12 = £360. Even if he only buys six games through the year he still ends up paying £51 more than me. Who's being robbed? Of course, you could argue that he'll have accumulated more games by the end of the year but to be honest, as long as I'm still getting enjoyment out of WoW, why would I play another game for any serious length of time?
What it all comes down to is the type of gamer you are. As a hardcore gamer I see something like WoW as an investment not of money but of time. WoW isn't something that I saw in the shop and though "Ohh, that looks good, I'll give that a go!" I thought about starting it for a long time the reason being is that I didn't want to waste my time with something that I wasn't sure whether I was going to like and that's what is more important to me. It isn't where my £9 a month goes, it's where my time goes and so far I've enjoyed my time in WoW alot, had some good laughs with people I'd never meet anywhere else. I'd consider that time well spent, you, on the other hand, may not.
It's horses for courses really. You think it's a waste of money, I, and 2 million other people, don't and ultimately I'd much rather pay to play the same game as those 2 million other people than play someone else's free but unbalanced, buggy, laggy and empty server.