Which is more profitable – an MMO with a monthly subscription or a free-to-play game?

The thing is, there aren't that many hardcore players. It's much easier to charge a fixed fee from all players than to collect large sums, but only from a few. Also, consider this: he buys the best gear, and then what? He'll buy more trinkets, but there's nothing else to buy. Meanwhile, someone else might buy only the essentials and perform just as well. A fixed fee is a stable source of income that will continue as long as the person plays. Even if he plays only 2 hours a day and, in another situation, wouldn't spend money on the best gear because he doesn't need it (and there are quite a few such people), he'll still pay the same amount as the hardcore player who, in another situation, would have spent a lot of money on cool gear.