Think about the uproar if it was more expensive for women?
In a nutshell women go on about equality in all areas of life, this is something I totally agree with. Infact in some areas it is advantageous to be a woman, the difference is you dont get blokes moaning about it (I tend to though).
No one should be disadvantaged due to their gender. Therfore there should not be a different pricing stucture for women unless the prize fund represents this difference also.