$70 and only 4 wires to solder. I've read on other forums that this will also allow you to play normal DVDs in your Gamecube. The only problem is that you have to take console apart and leave it open so the discs will fit. It looks like the same company that made the top-loading PS2 case is working on a full size replacement case for GC also though.
I know it's more work than PS2 or Xbox, but it still sure beats the shit out of that PSO/Broadband streaming method for playing backups.