I recently snagged up a little bundle of GBA joy from a local thrift store a few days ago for $10 (all loose):
-Blue GBA Advance with charger (with a goofy "Ratatouille" sticker on the top)
-Super Mario Advance
-Mario Golf
-super Mario Kart Grand Prix
-neat little zippy case that's not game related, but have no clue what it was originally intended for
and a bunch of kid games (Petz, The Incredibles, Over the Hedge, Cars, etc.) with a few sports (one of the Need for Speed games I think, two different years of Madden) to total 15 cartridges.
The GBA, sticker aside, is in immaculate shape for being a kid's system.
I swear I think Bira Bira wants me to continue to collect but with portable systems as that's about all I can get game time on these days.