Some recent serious games auctions on eBay:

Serious Sam: The Next Encounter (Sony PlayStation 2, 2004)

$7.50
End Date: Sunday Feb-4-2018 18:30:11 PST
Buy It Now for only: $7.50
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Original Xbox Serious Sam Video Game CIB -- Combined Shipping
$9.99
End Date: Monday Jan-29-2018 12:02:54 PST
Buy It Now for only: $9.99
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Serious Sam: The Next Encounter (Nintendo GameCube, 2004)
$20.00
End Date: Thursday Feb-8-2018 20:43:05 PST
Buy It Now for only: $20.00
Buy It Now | Add to watch list