Clint,
The rarest and most limited are runs done for companies or organizations. Some of less than 100 units. Usually used as awards or gifts for donations. I think one of only 50 314 trappers was done, and those had fancy emblem in scale and presentation wooden boxes. I believe it was a Wild Turkey organization. Companies have ordered small runs of pad printed or etched blades also, as employee awards. I think there is a minimum number now but I keep saying if I win the lottery we will have a 300Bucks jigged bone 303 made...ha
The most expensive will be some of the older David Yellowhorses, especially the custom made ones. Painted Ponies are up there also. Some of the old custom shop 300s made with expensive stuff like ivory scales and file work, etc. will be up there also. Other folks have done costly buildouts using high value steel and scales but the 300s usually aren't to attractive for folks to use that expensive stuff on, being just common ole slipjoints. There are a couple of odd production knives that I have never seen a close photo of or handled in person, but I am keeping my mouth shut on those, you will have to figure those out yourself.
300Bucks