I've seen a few for sale personally... turned out like me, they were trying to rebevel hard heads and couldn't get the job done with the original stones... and it takes time with hard steel to get it to change angle.
I h ad that problem too.
Ron fixed me up... made me realize its all about raising a "wire edge" opposite of the side I'd be working BEFORE I switched to a finer grit stone.
I was doing it ALL wrong. Wrong headed, wrong results!
some people are willing to learn and admit it "operator error" some not, so sometimes, they come for sale.
Those big holes in the Lansky alignment tool allowed it to change degree of angle considerably...and I gave mine away!
The KME is a precision tool... As Charlie said, It's not a purchase, but an investment...lifetime I might add!