For items that have postage i do think it is a shame to post them on a public forum, not out of selfishness but from the prospect that it takes the fun out of finding a good bargain and will also up the bid if people on this forum all see the same link and bid - pushing up the cost of the cage (and taking away the bargain factor..) Since this is a hamster forum and people are looking at ham cages say 10 see it and want it - we all know how far bidding wars can go!
Though i think for collection only this is a brilliant idea!