Record HD PS3 gameplay with capture card?

I was just wondering what the cheapest way to record HD gameplay for youtube with a capture card? I would like the total cost to be below $50. I have an iMac 27" So I should be able to handle all the gameplay and editing and stuff. Also I noticed when I looked at one online that it's basically just a USB wih AV input. If you plug in the AV chords into it, you won't be able to see it on the T.V. So I'm guessing I have to get a spliter? Please name all chords and the capture card specificaly please. Remember has to be HD and preferably under $50 (Cheaper the better but has to be HD haha)