Originally Posted by Aodhán
Can you name anything where the price is MORE than one is willing to pay? I hate to break it to you, but that IS that market value, that is ALWAYS what determines the price. Unless you enjoy having a lens for sale and not actually selling it.
Have a look at KEH's web-site, scan eBay (completed listings), look at places local to you - its the only thing that will give you a picture. Make sure you judge the shape of the itmes against yours, as that can affect the price greatly.