Sometimes the females sell out first, depends on supply/demand. Females lay eggs(even when they dont mate) so they require a little more care. Most panther chameleon females look similar and dont vary in color like the males.
Yeah, I would agree with what Warrix642 said. I think my female is cute and peach but most "non-cham" people who see her immediately ask "why is she so ugly?" and then ask if they can check out the male because he has colors. I think most people who buy females are people who are really into the keeping of chameleons and breeding. Most people who want a pet don't want to put up with egg laying and would rather have something that looks "cool" to them.
Males are larger and most of the time they look better, like in the case of a veiled chameleon. And they also live longer because they don't have the strain of laying eggs.