First off I will open with I don't have a clue because MM or MMr is a game well beyond the price range I can justify for "toys" that rarely get played in our house but I think you "missed the boat" unless you bought that machine fairly cheap.
I would look at the math like this: MMr cost around $9000 and you have a "brand new machine" has driven the prices down to around the same point for nice originals. Assuming yours is decent overall and someone just has to install a playfield, plastics, and a few other odds & ends to make it nice I would think somewhere in the $5000 to $6000 range would be a "fair" starting point.
The someone willing to do the work could invest a couple grand and have a fairly nice machine for $7000 to $8000. As it sits anything over $6000 is likely a stretch and less than $5000 just seems way to cheap. I am sure others will chime in shortly!