The first words out of your mouth should be "how old is the skin?". No matter how good everything else is the boat lives or dies on the state of the skin. Skins are very expensive (at least they were last time I checked which was a few years ago)because they have built in floatation bladders. But an old frame with a brand new skin can be worth a lot of money. Frame design has been stable for many years so there is a lot of interchageability across many decades.
In recent years all the first line folders have increased markedly in price.

: I have a line on a used Klepper kayak. I don't know the details yet
: but I am pretty sure it is an older boat. Never seen one in
: person and just wondering what these sell for? Yes, I know
: condition, size, model ect. are important..... I just don't know
: anything yet. This is not that close to me so I am trying to get
: some idea of what they are worth so I can decide if I want to
: pursue this.

: Thanks in advance.
: Jeff