Doc, most of the difference in pay between genders can be explained by the type of jobs each gender end up doing, rather than discrimination.
Women have a lesser tendency to go into engineering and business, which can lead to high paid work and more a tendency to head for health care, social science, arts, etc. Still in 2007, there's less than a quarter of women in engineering schools, its not the men who force women not to go there.
There's also the fact that until lately, the number of working women was less and initially women were less educated than men, which means they worked on average less years and started lower. Also, women, since as you said it, value work less than men tend to choose less high stress, much overtime work, and choose more part time work (I am not counting those forced into part time). They also choose less shift work and dangerous work.
There are factors like women being single parents more often that impact work, but not sure how much you can assign this to discrimination. Even if the guy wanted the child, judges would give it to the mother in most cases. At least there is an increase in shared custody, which mitigates this.
All that put together, and some other things, explains most of the difference in pay between men and women. There's certainly X% left (certainly less than 10%) of out and out discrimination, like some female job categories similar in relations to generating value as male job categories, with no difference in qualifications needed, but still getting lower pay. Those differences can take a long time to work themselves out, but economic pressures will even them out eventually (with the constant pressure on profit margins, no company wants to pay more than they should for anything).
An woman engineer or business graduate today, still faces some entrenched resistance from dinosoars, but there's a good chance her salary at the end of her career, if they follow similar paths, will be very close.