Are HEP restored originals really still worth $3-4000 more than a brand new remake?
That seems pretty crazy to me. If that is true, then there probably really are enough of the collectors who prefer originals. That might keep the price of average machines up a bit. It is definitely weird to be talking about MM in the same price range as other 90s pins. WH20 can get over $5k in unrestored condition.

If I had an original MM, I would probably list it around $8-9k. If you are not in a hurry, it may pay to wait and see if someone will pay it. If you find a buyer who hasn't been keeping up with stuff for 5 years or so, that may seem like a really good price.

If CGC releases an upgrade for MMR to use the large display in AFMR, I would imagine the demand for an original MM would drop a bit. The intent with MMR was to create as close to the original as possible, so it is a good comparison with an original. The added features they are doing now on AFMR make it a better game. Yes that is my opinion, but I really do think it is better, and I really liked the original game.