I play WoW too. But it is fundamentally different from Magic Online. In WoW you pay a monthly fee for the complete game, including patches. Anything you want to acquire in the actual game comes at no extra cost only limited by time and effort spent.
Magic Online on the other hand uses more of a micro-transaction (I hate them) based system. You gain the basic gameplay for free (or a smaller fee) and must buy each thing you wish to use in the game. You can't just try to find item x, you must buy it.
The effects are clear: The first game has a fixed monetary cost and an open ended effort cost, while the second one has no effort cost and an open ended monetary scale.
Edit: A good read about the effects of the second implementation can be found here:
http://www.danwei.org/electronic_games/gambling_your_life_away_in_zt.php
I can agree with the notion of paying for services. I can't agree with paying extra for mandatory ingredients of a package, especially if you must pay a subscription fee already.