One thing that often surprises people about these things is the sheer size. Yeah, it's smaller than the standard 101 key Model M, but it's still nearly as large as a 104 key Filco. These are NOT small keyboards, even if they are tenkeyless.
I do agree though there are more out there than it seems from the rarity on ebay. These things were often used as rack mount keyboards. Anyone here a server admin? When was the last time you changed your server keyboard? I know in the server room across the hall from my office there are 4, for instance. Practically unused. Most of the admins prefer to use the serial console in the front of the room to admin the servers, but the keyboards are there. And no, I can't get them...I've asked. I've even offered replacement rack mount keyboards, but no dice.
Their take: why should we even consider pulling them off the KVM? They work, they will work until the building falls down around them, so what's the point of swapping them?
Then again, we also have a full size 200MB IBM HDD sitting in there, sort of on display. I'm talking about the massive ones, that you needed a cart to move around. So maybe I'm wrong about how many are out there in the wild.