Interesting idea about the outside situations. Having a spouse/partner who earns more might make money less of an issue, and I'd imagine that women would be in that situation more often than men. That particular asymmetry is probably shrinking, so maybe this is one of those differences that will become less important.

One interesting thing to note: the gender difference in propensity to negotiate was huge in the first Boggle experiment (a factor of 8) and went down to a factor of about 1.3 when people were told explicitly that the payment was negotiable. If indifference to money were the explanation, it seems unlikely to me that you'd have so big a change in behavior from such a small change in the setup. The author's explanation of gender differences in cultural norms/rewards or some testosterone-fueled jockeying for higher relative wealth sounds like a better fit to me.

I haven't heard anything about initially high wage levels leading to lower raises over time. Even if it did eventually lead to the same salary as your peers, you'd still be ahead overall.