Bear with me, I haven't played EVE and don't really ever intend to, but I am a bit curious about the inner workings.
From what I understand, the in-game currency, ISK, can be purchased with real money, and ISK in turn can be used to pay for monthly membership fees. The really committed players, presumably, have quite a bankroll of ISK at their disposal, are the highest ranking members of corporations, etc. They're also the most likely to maintain accounts year over year, and the players most MMO developers would rely on for revenue. EVE, however, lets them pay for their time with in-game money.
Without income from the super-committed, CCP would then need to instead rely on the casual players and the curious players that tend to only stick around MMOs for a few months at a time, making for an incredibly unreliable revenue stream.
It sounds like a recipe for failure or bankruptcy, but then, that's just my perspective as an outsider. What am I missing?