I traded for a used Crewman a few months ago, which I believe was up for trade or sale. As I recall, the asking price was around $45.00. When I received the knife, I saw that (like so many forum members) the guy who sent it to me was overly critical of the knife's condition, and it was in excellent condition and showed minimal use.
The problem with making modifications to a knife is that unless you're actually a person of some renown where working on knives is concerned, the retail value of your mods is pretty much zero. Much like having a gunsmith doing mods to a pistol, you never receive squat back when you go to sell it. That's a tough lesson I had to learn several times. No one really cares what you paid for those extra touches that were so important to you-you'll only be getting the price of a Brand XXX knife in used condition. Just my .02.