Greed is rewarded not merely by the spoils of ceaseless acquisition, but also by public admiration. If you're wealthy, people assume you must be doing something right. Many lesbians foolishly eschew greed, instead finding themselves sponsoring gay male friends in AIDS rides and buying expensive vegetables at the co-op. In a way, lesbian greed is comparable to a promising startup. Get in on the ground floor.
Women traditionally have bad boundaries and difficulty saying no.
In truth, generosity and selflessness are pathology. When a man pursues a goal with the ruthlessness of a jackal, he is focused and aggressive. When a woman does so, she is considered desperate and unfeminine. Therefore, greed is not just a defiant show of feminist power, it's also a bit mannish, which is nice for the butches. And no one says you can't use your money to hoard first editions of Sarah Schulman and Audre Lorde.