Condition usually sets the value for a particular truck. Now that is said its "my opinion" that there are more folks looking for the "pickup" to fix up as a daily driver.
I love them all, and would like to have a big truck but I also know some of the parts, depending on what year, can be hard to find. However, if I saw a big truck in nice shape I'd wouldn't hesitate to offer or pay a fair price.
To be honest, I don't think there are enough big trucks swapping hands to get a good feel for it. Depending on CONDITION they usually go for less money......in "my opinion".
.....now lets see what the rest of the guys say!!