EyeTV USB Wonder 2.0
I just bought the EyeTV USB Wonder 2.0 by ATI, and it works pretty good. I purchased this one because it has zero lag, so I can hook my PS2 up to my 20" iMac G5 and it looks great!
The other EyeTV units have an MPEG encoder built into them, so there is a one second delay in getting the video to your screen, which makes it useless for my gaming needs.
As for Hard drive space, it varies depending on the quality you set the recording at. Since this unit doesn't have the MPEG encoder built in though, my Mac has to do the encoding, and you need a dual G5 to record at best quality, which takes up about 1 gig/hour. My recording are set at VCD quality, which only takes about 400MB or something an hour, if that. The picture quality isn't great at that setting, but it's good enough for all the wrestling I watch.
In live mode, the picture quality is great, especially with the video games or anything hooked up to the composite or s video input.
As for your question about cost, all you need to buy is the unit and that's it. It comes with the software that you need, except for Toast is you want to burn your shows to DVD. But I think you can use iDVD for that as well. Hope this helps.