As far as I can tell, this is legit (check the crazy terms and agreements here - of course, they got the hymen aspect totally wrong). Trailer:
The homepage is here.
Currently, the highest bid for Catarina is $450,000 - the highest bid for Alexander is $2,500. This massive difference is not surprising. If you rule out attractiveness, there are likely two other factors at play: (1) men's interest in, and willingness to, pay for sex; and (2) that women's virginity is considered a much more valuable asset than men's.