Praxius Praxius:
Well as I said, I'm no expert on the whole MMORPG or whathaveyou games.... from looking outside-in, it seemed to run along the same basis as Second Life (Which I only tried for maybe half an hour, once, and then uninstalled it)
Guild wars would be a better example. 2nd life is free and relies on in game purchases to support the game whereas Guildwars is a more traditional one time purchase with unlimited access after. You can buy extra items for money but they are not game breaking. World of tanks also is a free to play game that you can buy equipment and tanks but they do alter the game and you can become a wallet warrior.
With each of these games it comes down to the user base and community. Some people will pay a premium in order to be a part of that. You can do a little of that in games like 1st person shooters that are team based but they are not the same sort of experience as a world with ongoing conflict and shifting battle lines and alliances.
Guildwars was also made by the same people who started WOW and split when they charged the monthly fee. It was a choice WOW made in order to create a much larger world and content with a much shorter development cycle to support a much larger user base. Guild wars does rival WOW in content but WOW comes out with more, faster and on a more consistent basis and delivers it to a much larger player base.