I've had a great time doing the cheapass thing with the Cube. I've gotten
Platinum cube + controller = $99
Mario Kart = free with bundle
Zelda: Wind Waker = $0.88 (new, Target with $15 coupon from bundle)
Platinum Wavebird = $30
251 Memory Card = $18 (new PM w/ Target at BB)
Metroid Prime = $11.50 (used, EB B&M w/ Edge card)
Eternal Darkness = $4.50 (used, EB B&M w/ Edge & B1G1/2)
TimeSplitters 2 = $10 (new, BB)
Harry Potter COS = $7.50 (used, EB.com AC)
Super Monkey Ball = $13 (used @ pre-played)
Animal Crossing = $15 (new, CC)
59 memory card = free w/ Animal Crossing
Super Smash Bros Melee = $15 (new, CC)
Zelda: Collectors Edition = $35 (used, EB.com AC)
GBA cable = $8 (used, GameCrazy)
2 Gray Wavebirds @ $16 (new, KMart clearance w/ Metroid Prime)
(2 Metroid Primes = $20 credit at Gamestop)
That adds up to $299, less if you subtract the Gamestop credit.