Yeah, I'm not exactly sure what the OP meant by "can't afford her". I presumed they meant the man in said relationships didn't feel like he was contributing "enough" to their purchases/commitments as a couple.... not necessarily things solely for her; I'd never agree to the idea that a man should feel like he owes her (or me) anything. The best gifts someone can give of themselves have no price/monetary value to them.
A lot of my other close friends from school are facing these issues too though. Initially, he is comfortable with her income and financial contribution to the relationship. After some time when things become more serious, he isn't comfortable taking vacations, buying groceries, marriage and planning a future together. He'll say he's guilty, jealous, resentful, uncomfortable, ashamed...when she on the otherhand is perfectly fine with their situation, and what he contributes. Mostly because she can see that the contributions you make to eachother are more than just financial.
Anyways, I don't want to come off as someone who typecasts all men as being the same way...I know I personally hate it when people make blanket generalizations. Of course there are great men out there who would be happy to be with a woman with a strong education/professional background. Still, it is hard, being someone that can take care of herself...but looking for a companion/love that shares the same values/interests/goals/ambitions, etc. who is able to look past the social stigmas. 😉