It all depends on if it is a true NOS versus a reproduction, if there are any production problems with the playfield, (dust in clear, registration, color saturation, etc...) that will also effect the price even though the playfield has not been used.
It also depends on how popular the game is that is is going in. The higher the value of a game, the more value the playfield has.
Example: A true NOS AFM playfield is worth way more than a reproduction. I remember some selling for close to 1800, while a the highest for a reproduction was about 700-1000 depending on time between runs. When somebody gets a top end restore job, NOS is preferred and people will pay top dollar for one.
95% of the time when you see a reproduction for sale north of 1k, the person bought it for the 700 price when they came out and just have sat on it until the supply has run dry.
I have seen a TOTAN and CC NOS sell for 2k, you will never see NOS Popeye sell for that much as an example.