Why do women get tons of men to pick from even if we're dirt poor and men can get tons of women only if they're rich?

It's biology. Men can have an unlimited number of sexual partners and one man could theoretically could father thousands of children. Women, on the other hand, have a significant physical investment in child bearing, and can realistically only give birth a few times during their lives. So women have to be more selective with their partners than men do.