The market for clarinet mouthpieces is very peculiar. There are brands which tend to be very valuable while others less so, but a poorly maintained Kaspar or Kanter is worth less than a superb Pyne or Bay. The "creme de la creme" of mouthpieces were made on a fine rubber blank which was made by the Chedeville company from the 20's to the 70's. Their quality does vary, and there were some other very fine blanks made during that time (Bettoney for example made unparalleled blanks which they included with their comparitively subpar clarinets). Ebay filled the unusual void by creating a national marketplace for these tempermental collectibles. It expanded the thought of mouthpieces. For example, prior to ebay, you would try a Kaspar, for example, from someone you knew or were referred to. You had a small window to decide if it was worth taking, and a seller would usually charge between $400-$600. Mouthpieces that warped, needed work, or were simply in less than perfect condition were disregarded. Everything has changed. With enough money and good timing, any person can own one of these vintage pieces. While they are still horded by some (I know three clarinetists who each have over 30 kaspars which they have been collecting for thirty or so years, and they refuse to part with any of them), most people now are able to search for something which suits them. They purchase a mouthpiece, possibly get some work done, and ultimately either replace their current mouthpiece or put the purchased one back up for sale. The downside to this is that mouthpieces lose their "charm." An informed buyer will tend towards mouthpieces which have had little or no work done to them, because the more work done, A. the less material to work with, B. the less it resembles the original product. Evrett Matsen, for example, was a wonderful mouthpiece refacer. By chance, his equipment was not perfectly symmetrical, which made is facings slightly unbalanced. Yet this imbalance came to be a desired trait which few have been able to recreate. Refacing a mouthpiece after Matsen worked on it would remove that nuance. The mouthpiece market on ebay also has its ups and downs. Sometimes vintage mouthpieces flood ebay. This actually is not very predictable. Sometimes, this leads to a drop in average sale price. Other times, similar to the way car dealerships actually try to sprout up in "colonies" to increase visibility, this motivates people to watch the auctions much more closely and more bids are placed. Similarly, "dry markets" react both ways. When buying a mouthpiece on ebay, read the entire description. Ask for pictures if not included. Any tip damage makes an item worthless... meanwhile, signs of wear (calcium deposits or discoloration) often times means it is a very good mouthpiece which was used frequently.