This is the Greenspan argument. In his own words:

> I always valued men and women equally, and I found that because others did not, good women economists were cheaper than men. Hiring women does two things: It gives us better-quality work for less money, and it raises the market value of women.

But in order to arbitrage this, you have to be willing to pay women and men differently. It's not impossible to see a market where everyone internally values work equally, but believes the market does not, and thus all lower their offers made to women.