I would ask in the Blade Discussion Forum itself. There's nothing wrong with trying to get an idea of what a knife or type is going for even if you are interested in selling it, and don't want to undervalue your offer or ask way too much, either.
As long as you understand that "value" can be a wild variable. Some experts can tell you what a particular model has been going for, but the market can do funny things to prices.
Unlike cars, for example, there is no real book value on knives.