Some recent serious games auctions on eBay:

The Serious Sam Collection Xbox 360 New Xbox 360, Xbox 360

$17.19
End Date: Saturday May-27-2017 20:45:30 PDT
Buy It Now for only: $17.19
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Serious Sam Collection (Microsoft Xbox 360, 2013)
$14.85
End Date: Saturday May-20-2017 8:11:41 PDT
Buy It Now for only: $14.85
Buy It Now | Add to watch list