Earlier quoted context omitted.
If women are underpaid because they're (consciously or not) undervalued as workers by entrepreneurs, then those same entrepreneurs are unlikely to visualize a net salary savings. You're basically saying: if women are as good as men but you can pay them less, why not hire women? And the answer is that the same factors that lead to women being underpaid lead to not seeing them as interchangeable hire with males.
I could be wrong, but I think the point that the poster was making was this: Sure, maybe women are undervalued on average, but that's just on average. Assuming women are both paid less, and undervalued, then together that creates a double opportunity for an employer that can see through the undervaluing, and rationally hires mostly women because they are just as good but cost less. And the point is that we don't seem…
Evidence? First, "pricing is information". Second, Uber et al, and the continuing follies of the tech industry demonstrating systemic sexism. Third, continued use of the word "meritocracy" despite repeated demonstrations that tech firms practice a particularly narrow form of geek clubhousing. Bottom line: no one's actually rational enough to exploit what's really a fairly transparent, backhanded attempt to say that women are paid less because they're worth less. We just tell ourselves that we are.