Figure more for couples, threesomes, and all that tasty stuff, but surprisingly niches such as shemales, adult BBW web cam and even lesbians don't usually cost more than standard camgirls.
Except for new models that always charge less and the Happy Hour that I've already mentioned, in most cases the rule is: Tore you pay, the hotter the action. Just charge it through CCBill, Epoch or use your sexcams Paypal account and it'll be your little secret anyway.
You can go for a cheap webcam sex site, where the average price per minute is like 0.90, BUT the chicks are gonna be shyer than a big-eyed 19 year old Mormon girl who never left the dairy farm.
So, getting her fingers to do the walking, instead of all that fucking talking, is gonna take a while. Unless you're into shy babes, and there's nothing wrong with that, hell it's a clean and harmless fetish, I suppose.
If you though the women were stripping for free, I am sorry to be the barrier of bad news.