I don't know! It's irritating, though, isn't it? I've noticed they're more expensive than male condoms just about everywhere you look. Probably they're more expensive because there isn't as much of a demand for them, so there's not a whole lot of competition driving down the price.
They're relatively new and there's not much of a market for them yet. Also, there is only one company that produces them, so there's no price competition compared to trojan/durex and the like.