I hadn't noticed ladies bikes being more expensive than mens, if anything I found more deals on women specific bikes, but I didn't like any of them.
I was told women's bikes tended to be shorter than mens - but my hybrid is actually longer than my husbands road bike -obviously they're not the same bike so that probably has very little to do with anything, but I happened to notice mine won't fit in the same space as his.
I bought a "man's" bike and it's much more comfortable than any of the women's ones I tried. That may have something to do with it costing about £300 more though.