True, Steele"s "Ebay Market Watch" does not take into account the condition of the microphone sold.
As anyone who frequently scans Ebay knows, given Klaus' example of an RCA 77DX, that these things show up pristine and original, refurbished by known RCA microphone restorers, to beat up radio station cast offs to total trash, sold with missing parts, some just empty shells, etc.
I liked it more for the "original selling price" column.
As one who keeps track, particularly of RCA ribbon microphones, I saw the 5 thousand dollar plus 77DX. I even saved the pictures from the auction.
It was brand new, in a sealed box, fresh from the factory, with everything, including the tags and documentation.
Others in much worse condition have sold for less but some with provenance sell for more than 3 thousand dollars.
"So and so owned and sang or played into this particular microphone" is the usual claim, often backed up with pictures, letters etc. which may or may not be genuine.