You're right. There are few used Herron Audio components for sale even though there are thousands of units out there. Could it be that the owners are so satisfied with them that they find few other components good enough to replace them? What I've seen in the used market is that the few used Herron Audio components for sale appear to sell for a pretty high percentage of their original retail price, and they don't stay on the market long. Even the 20+ year-old phono stages seem to hold their value and disappear quickly.
But that's just my opinion. And observation.
But that's just my opinion. And observation.