I just finished up a playfield restore, coin door restore, replacement of the IDC connectors with molex crimp type, replaced header connector pins on all boards, rebuilt power supply, rebuilt playfield machinery, touched up and cleared playfield, cleaned all playfield parts, plus a thorough overall cleaning of the cabinet (sure found a lot of spare?? screws/nuts in this one) on a Jungle Lord. Kept rough track of the time involved 55-60 hours plus about $300 in parts (the sound/speech boards are New also and not included in the $300). Even IF this was game was acquired for FREE I would have a hard time netting $15 per hour, adding what I paid for the game to begin with makes the numbers much worse. I hope I enjoy the gameplay and am able to keep it for a while until I forget how much time/money was invested. No wonder most every early solid state game I have seen for sale has had the minimal cleaning, cheapest of repair/hacks possible done to it to call it working (most are just barely working). Even a so called shopped machine had only the easy to get to rubber rings replaced (if a screw or spinner had to be removed it was not), rusty/nasty leg levelers, caved in coin door.
I know I see some early solid state machines that are very clean that sell/are priced well above average but think that even these are in need of upgrading all the boards and connectors.

Yeah, pretty much eliminates the theory of "Find something you enjoy and make a living at it" from most pinball machine restorations. I still enjoy it and will do it again and again for the enjoyment. That is what a hobby is all about.