A National Semiconductor IMP-16C recently appeared on eBay. The IMP-16C was an early 16-bit microcomputer and was produced in small numbers (the item description says 100 were made, which is probably accurate). The seller also claims it might be the only one, but I doubt that. It might be the best surviving example, however, as it is working and in good cosmetic condition.
The final sale price was $5,500, an impressive price considering there aren’t legions of National Semi collectors out there.
Classic Tech 
I have one of these available now on eBay. Much less than 5k!
https://www.ebay.com/itm/276198259773?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=6f2Ysmt6SCa&sssrc=4429486&ssuid=6f2Ysmt6SCa&var=&widget_ver=artemis&media=COPY