Okay, I've just send them for appraisal at http://openforsale.com. After much consideration and advises, here's the Buy It Now (BIN) price for the following domains mentioned.

GamblingDen.net (NameCheap) --- $700
DavBeckham.com (GoDaddy) --- $40
XpertSurf.com (Enom) --- $40
2fair.com (NameCheap) --- $300

Payment mode accepted: Paypal