I just won another eBay auction for a used Tower set; $43.25 + $19.10 shipping — not a bad deal compared to $120 + $23.26 for a new one. Hopefully it will arrive in time for TCEP so that I can have multiple chain lifts. (Only the Tower sets use the chain elevator — all of the older sets use a screw elevator.)
All told, eBay has been very good to me when shopping for used Chaos Toy sets. Most of the sets have been in good condition (though not necessarily complete). Some of the sets have had extra pieces (which means that originally there were multiple sets that got combined and munged). The Intermediate set cost me $6.50 plus shipping — an excellent price compared to its original price of $100; each of the Master sets cost me about $30 (plus shipping) which compares well with the original $135 price tag.
Most of the sellers have (IMO) been underpricing their sets, but there’s one seller who has been overpricing: he’s got a single Starter Set (original price: $60) that he listed for $89.99 OBO, then $69.99 OBO, and now it’s listed at $39.99 OBO. In the meantime, larger sets have been listed and sold for much better prices.
[Edit: Now the price has dropped to $29.99 OBO; still not worth it for me, but maybe someone else will find it useful. In the meantime, my new Tower Set has arrived and is in good condition.]