Ah, I see, you're assuming that market forces are totally rational instead. I wish market forces were totally rational.
Let me spell it out for you -- you think that a 5-25% price difference in salary will make or break a business instead of such things as being first to market, getting lucky on a government contract, or buying the right or wrong start-up. Companies don't win solely because they have the right talent, there are a number of things that have to go right for a company to make it big beyond just talent.
Then again, you're also assuming that women are given the same opportunities to get up to the same skill level as male counterparts whereas this study found that the women were less likely to be considered for mentoring possibilities. Students don't cost mentors anything and there are far more students than mentors, so if there's a systematic bias against equivalent female students receiving equivalent mentoring opportunities then it would make sense that until that bias removed women may never receive the same opportunities in the paid workforce.