Key to this title is the backglass. If it is mint - with the reds etc not washed out, then you have a starting price of $2000. If the playfield and plastics are in 8/10 condition overall, then you have a $2200 - $2500 machine. If the game is reconditioned and working 100% it should sell for $2400 - $2750 with an Pascal board.
It is the most collectible SYS1 Game, and in a buyers market you should get at least $2200 for a decent game.
Untested will significantly lower the price.