That's definitely been my hesitation with pulling the trigger on an XEGS. I love the games on the A8/XEGS but the availability of reasonably priced carts is kinda disappointing. If you just want Donkey Kong, Missile Command, Star Raiders, Pole Position, and Congo Bongo your golden but if your looking for games like H.E.R.O., Karateka, Choplifter!, or Pitfall II be prepared to spend some cash. Even Orc Attack is going for nearly fifty bucks not including shipping. I love Orc Attack but not for $50 bucks.
http://www.ebay.com/itm/ATARI-Orc-At...item27ef3ce7c6
On the upside Blue Max & Star Trek SOS are going for less than $20 though. Until I pick up a reasonably priced XEGS I guess I'll go on collecting C64 carts. Recently I added Choplifter and Buck Rogers to my 64 cart collection.