These were expensive when released and were not well receiced.  Value has plummeted. You be lucky to get $10.00 IMO

I bought a set on ebay for about $15 last spring and was happy to find it.  I followed DF auctions every week for months and only saw one or two sets up.  But the demand was indeed low.  

The little promo dart lizards that came with pre-order of one of the lake tile sets are in higher demand.  I think I have seen them do about $50 two or three times.  And, they are addictive little things to play with.  Even a two year old can understand trying to walk a figure across a bridge and having lizardmen pop out of the water with blowguns!