Sorry comrade, you seem to have missed how the market economy works!
"Fair value" is precisely what the market decides - and if you BELIEVE that too many people are selling above fair value, and too many buying above fair value - guess who is wrong?
It ain't the ones buying and selling (ie: the market), it is YOUR expectations of the market.
Why pay US$750? Because there is NO NEW HARDWARE.
There will be NO NEW HARDWARE (of note).
Supply v demand. Supply is small, and dwindling as components die with NO new manufacture and limited repair options.
Demand is growing, as more people rediscover their computing origins and now have the means to obtain that which they could only dream about in their youth.
Get used to it.