Equal Wages?

Alright,

This probably isn't the place for this discussion, but thought i'd raise it anyways. Women want to get paid the same as their male counterparts for the same job. Fair play, you might say. Why shouldn't they? Its only a chromosone difference after all.
I would like, to rather contraversially, say that I don't think that they should both get the same wage at all. Picture this. Susan and Gary both work as senior managers for some company. They both earn 30k and are both happily married. From the company's point of view, that can't be right. When Gary was first appointed, he came with a guarantee. He is guaranteeing that he will work 365 days a year, except ill days and holidays. When Susan gets employed, she is guaranteeing that she will work when not ill, on holiday or on maternity leave. Thats a huge extra. In a worst case scenario she could be not working for an additional 6 months every year compared to Gary.
Obviously that is a worst case. In an average case, where she has 2 children during her 15 year spell at the company, thats one full year not working (based on 6 month maternity leave per child). That means, that she should get paid 1 years salary less over the course of the 15 years. Thats 30k/15 which is 2k. Gary should earn 30k, she should earn at most 28k.
What are your thoughts?