The most dangerous thing a knife collector can do is leave a list telling an heir what he paid for his knives. With such a list an heir can price everything a certain percentage above cost, and the astute dealers will cherry pick everything that the market has taken to a high level and those will be gone quickly at a low price, while the losers will hang around forever.
Coupled with the knives that have appreciated will go too cheap, anyone else that tells the heir the reality of the losers will be looked upon by the heir as a thief trying to steal the remaining loser knives at far below their fair market value. After all, the heir has that original list.
All which goes to my mantra -- knives in the aftermarket HAVE to bring aftermarket prices. What the collector paid for the knives at the time of purchase is immaterial. Knives are like stock, the prices will go up on some, will go down on some. The advantage of selling an entire collection at once is they will average pretty well.
Almost as dangerous as keeping a list for value is anyone who is not keeping up with the market on a regular basis trying to sell the knives themselves, for the same reasons as outlined above.
Just after I sold Blade Magazine years ago I got into saltwater fishing, and wanted to get a boat. Seeking professional advice I asked Phil Lobred, a former Alaska fisherman in the days before the TV shows.
Phil asked how far I lived away from the ocean. (8 hours), how much I enjoyed trailing boats long distances, how many times a year I would be going to said ocean, and then he really hit home. "How much do you know about the water you're fishing? How much do you know about where to go and what to fish for depending on the time of year, the water temperature, the weather conditions, and how the overall trend of fishing is going on locally?"
"I know none of that," I answered. He nodded.
"I think you you should consider getting to where you want to fish, hire a professional guide who is fishing nearly every day in the area, pay him what he's worth. When you finish fishing you step off the boat and go home while he handles the boat clean up, the boat storage, and the maintenance. And you're going to go home with a lot more fish, and save a lot of money."
Phil Lobred is a smart fisherman, a nice guy to share such wisdom, and a top notch knife collector as well. Everything he said can be applied to selling knives, in my opinion.
