When I consider a multiple pinball deal, I typically put a fair value to each machine. If the sum of the two values is equal to or more than the deal amount, then I typically move forward with the deal.
If the sum of the two values is less than the deal amount, then I have to reconsider the deal and determine if I really want the two games to the degree that I am willing to overpay.
So for your deal, you have two machines.
I value Phantom Of the Opera as a $1,000-$1,500 game with $1,000 being average shape & $1,500 being very nice shape.
I value Big Hurt as a $800-$1,200 game with $800 being n average shape & $1,200 being very nice shape.
So in the condition described, I would expect to spend around $2,500-$2,700 if I were buying the games individually.
So for me, the $3,100 price tag is too high.
My values are my own, so you would need to consider your local pinball market and determine your own value for each machine individually.
But my advice would be to negotiate as I feel that you are overpaying by at least $400.
Good luck!
Marcus