Yes, its collectible because GameCube is becoming much pricier all across the board, and it's a really solid game. Also Skyward Sword was a huge success, and a lot of gamers who were introduced to the series with Skyward Sword are looking for more Zelda. Check out Ocarina of Time and Majora's Mask, the cheapest MM BIN right now (besides a broken one I have listed) is around $26 shipped!
Same thing is happening to a lot of GC titles, I've been selling Smash Bros. Melee, Paper Mario, Mario Sunshine for $22-$25 each easily. Even the slew of crappy kids games tend to go for $8-$10 each.
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