When men's incomes go up, everyone expects the demand for wives to go up as well. If average male income rises, men have to offer women a piece (maybe a large piece) of the increase if they want to attract a wife.
But when women's incomes go up, lots of people expect the demand for husbands to go down: "Once women can become financially independent of a man, they will choose to do so."
This is theoretically possible, but only if husbands, like potatoes, are inferior goods. Counter-intuitive, to say the least. How many women dream of becoming affluent cat ladies?
If you distrust intuition, take a look at the facts. Back when women's incomes were low, men who wanted to get married had to be ready to shoulder, say, 90% of the financial burden of the household. As women's incomes have risen, the fraction of the burden men have to carry to marry has plummeted. This is just what you would expect if rising female income raised the demand for husbands.
So what's going on? I can easily believe that some kinds of husbands are inferior goods; a high-earning woman might rather be a spinster than marry a high-school drop-out. And there are symbolic margins along which men get a worse deal than 100 years ago - modern males are probably more afraid to make sexist remarks within earshot of their wives. But if you take a look at how much income women deposit in joint checking accounts, it's hard to avoid the conclusion that demand for husbands is at an all-time high.