Grading Guidelines for Reel-to-Reel Tape

Anyone out there know if grading guidelines have been set down for reel to reel tapes? If so can you please point me/us to those grading guidelines.

Doing a web search you can find vinyl grading guidelines, but none for reel to reel...

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They have reel to reels on, perhaps they have suggestions.
None that I know of, some are selling R2R media at crazy prices without even play testing.

But R2R tapes are so hot right now they are getting away with murder on pricing!
You think so? 

Like what are some examples?

71/2 ips tapes if in good condition can boarder on a spiritual experience. Can’t put a price on
Nothing I agree with at all on r2r pricing but just take a look on eBay at some examples.

$200 to $500 is not uncommon for "in-demand tapes".

And they are selling.... Crazy but true.