Well, although it could come across sexiest I do think the prices are right. Women need a lot more care for their hair (this is generalised by the way). Men 'tend' to have short hair and just need a quick snip to stop it getting in the way, even if a women just wants a quick snip the hairdresser still needs to show more care and perfection into making sure that snip is just right.
I'm sure if a guy had really long hair and wanted a full colouring package with blow-drying and washing involved he wouldn't get away with paying just 9.95 for a several hour job.
As with the girl you're describing, it could work both ways and I wouldn't really know how to reply. Since she was a women I think the hairdresser would have put more care into it, a man just needs it all shaved off, but the hairdresser was still probably cautious when cutting the women's hair. Sorry if I'm rambling (I do that), I hope you can make sense of this answer.