condyk wrote:
Lenses are worth what people buy them for at any given time. Values change according to many factors. The 24-105mm impqact on 24-70mm prices is one example and there are many more. I probably wouldn't buy a used lens more than a year old personally but I'm sure many do and get good value. L's are advertised at high prices but often we see them sitting there for a while. We never know the sold price. I haven't lost overall on mine but I buy at very good prices and not usually new. It also depends on the specific model.
Lenses are worth what people buy them for at any given time. Values change according to many factors. The 24-105mm impqact on 24-70mm prices is one example and there are many more. I probably wouldn't buy a used lens more than a year old personally but I'm sure many do and get good value. L's are advertised at high prices but often we see them sitting there for a while. We never know the sold price. I haven't lost overall on mine but I buy at very good prices and not usually new. It also depends on the specific model.
What happened to the price of the 24-70 f/2.8L? I bought mine a year before the 24-105 came out from B&H for $1139.95 and now it goes for $1149.95. Are you saying that the introduction of the 24-105 f/4L made the price of the 24-70 f/2.8L increase? 
Maybe you were referring to the used market?
