It's all a bit of a rip off to be honest and trust me I know from experience. You essentially pay money to wank. In the grand scheme of things, that's what you're doing. You get charged per minute, some girls charge more (in some cases A LOT MORE) than others and private mode is always dearer than group mode as you would expect. I used to do it all the time and would always kick myself afterward when I realised that I had just spent £85 to wank and chat with a girl, whereas for £15 less I could have gone and had a cracking 30 min punt.
I promised myself a while ago that from now on the only time I'll use DirectCam is if the gorgeous Georgie Lyall is online, that's only because I am a massive fan. And she's hardly ever online anyway these days so there's not much chance of me wasting money on her.
Honestly take it from me, don't get into the whole webcam thing, it is very enticing seeing all these gorgeous girls that you can chat and flirt with but always remember, they charge by the minute and they will keep you on there for as long as possible knowing fine well that every minute that passes is more money in the bank for them.