Putting things into perspective, a lot of people spend a lot of their time playing a single game rather than buying one game every few weeks (I used to do the one game every few weeks thing until Diablo1/2 and WoW). I, myself, played WoW for over 2 years and had quite a blast playing it with my friends online. Had I still been doing my old practice of play-finish-buy again, I'd have ended up spending at least 100+ dollars a month in games (as my old practice was also to keep trying out games til I find one I like then putting everything aside til I'm done with the game I'm into at that moment- I know it's not the most efficient way of spending one's money, but I make a good living so that a few hundred USD doesn't really bother me in the least). One can say that even with it's monthly fees, WoW saved me at least a hundred dollars a month.
There has also been times wherein I haven't the time to grind out or farm gear (due to time requirements for work and relationships) where I just decided to buy the gold I needed to support my need for pots/mounts/repairs on my character or to quickly gear up an alt. 50 bucks to make my life a ton easier and to allow me to spend less time farming/grinding seems a lot logical than sitting in a PC for 6-10 hours doing (IMO) un-fun parts of the game just to sustain the times I get to play the fun parts. That and the fact that I make more than 40 bucks an hour working means that it would have been much more efficient to spend the 6-10 hours working instead of playing...
Anyway, what I'm trying to say is that I think it's all just a matter of perspective and a person should be allowed to use RL money if they want to.
I understand the concept of playing an MMO for a long period of time with the occasional new purchase of the latest game, opposed to buying a few new games every month. It does save you money, and I love to use that in arguments where people say " I can't believe you pay to play a game!" I have been thinking about getting back into WoW actually. However, buying all the new expansions is a little daunting to my check book.