I definitely understand that mindset.
I think with pay-for MMORPGs you have to just be sure to find ones that make it worth the investment. The sheer amount of work that goes into WoW can help ease the blow I think... but on top of this, the users receive regular updates to the game. Not just bug fixes, but new options, quests, areas, etc.
WoW might be $15 a month, but even before the expansion pack it had increased significantly in content, modes and the sheer amount of places to go.
The same is true of LotRO. They've added player housing, refined the raids, adding player costume op