Aaaagh, good old supply and demand
The forums here are only a microcosm of the knife world. Case knives for instance probably have more collector interest than any other brand in the world, but they do not generate much interest here.
BF/KF tends to be more oriented to the "tactical" and "outdoors" crowd and not to traditional pocketknife or art knife collectors. The relative interest a knife generates here should not be taken as the sole authority of its popularity. I remember a Richard Rogers pearl knife being for sale here recently and it was not "bought immediately." His knives are very much in demand nationally and he seems to win the Blade show "best handmade knife" award every year now. The fact it sold slower than say a Steve Ryan or Ken Onion would here only means that Ryans and Onions are more popular on BF...
I will agree with you though, there are makers whose output seems to outstrip interest in their knives. Part of that could be design related or quality related. You can not rest on your laurels in this business. Overproduction can also be a cause.
The question posed by "underdogizhere" is a good one. If a custom maker has a quantity of the same knife floating around (10, 25, 200?) what determines its secondary value? Well, if it is a series of 25 and there are 26 eager buyers than the price will be good. The larger the production numbers are of the same knife mandates there must be a corresponding increase in the number of eager buyers to maintain its value. The use of manufacturing aids (CNC, lasers etc) throws another wrinkle into the equation
The maker must balance his needs to make a living with the long term (ie higher resale prices = higher demand = more long term business). There will always be a temptation to produce more as custom makers only make money when they first sell a knife. Secondary prices are important to the wise maker, but that does not help him buy food, shelter, and clothes now.
The last thing to consider is that the prices of knives (or any collectible) are highly volatile and can be easily manipulated. The world price of pearl handled knives was driven up by the collecting habits of one man and his death "crashed" that market. What if a collector was faced with a sudden financial crisis and was forced to sell off his collection of 20 Ryans, 20 Emersons, and 20 Onions all at once? Would this have an impact on secondary prices? Something to think about.
Good thing I buy knives as "users"