What jawanda says. If your spots were not skimmed, the site would die. Would you rather it be a 500k site with skimming or a 200k site with half the galleries not skimmed? Think carefully before you reply.
I've only ever seen one TGP that actually sells traffic on a price per K basis. Everywhere else sells you a spot, so traffic depends completely on your thumb/description, day of the week, trades etc.