The Q Game Boy Player is LUDICROUSLY expensive. I've only ever seen one on eBay, and that was a Buy It Now auction for around US$500. YES.
Seriously, give it up - it's a lost cause. Besides, the things look damn ugly. If you really need to play GBA games on your TV, I'd recommend either that third-party thing that goes in the Cube's memory card slot, or a Cube and a Game Boy Player. You can still buy them bundled, can't you?