I'm not surprised by this, since this game is basically Diablo 3. When D2 came out it sold so many copies that it actually changed industry standards for computer games sales.
There were so many players that not only did we bring battle.net down more than once, San Francisco players crashed our local broadband internet provider the day D2 was released! HA, take THAT SBC!
-420
EDIT: Oh and that store needs to wake up, the 20 copies were probably all taken home by the staff. Comp USA has an ENTIRE WALL dedicated to Guild Wars boxes.