It is like anything. You can take it as far as you want. Also how much of the work are you doing yourself? I use as much of the original machine as I can because I like original. I do my own board work (with plenty of advice) and touchup existing playfield and do the clearcoat. There are still plenty of costs in flipper rebuild, sleeves, rubbers, bulbs...., broken plastics and posts. Those add up fast. That being said I have about 2k into a restored Diner. That is about my average including the machine, but I don't buy high dollar machines.