Lots of good advice in this thread!

I'm looking at these restoration projects from a retail business standpoint.

I've said it before... all the Bally/William's from the 80's (and the Sterns from that age, and the Gottliebs for that matter...)

I no longer take, even if the machine is offered for free.

Machines this age take an extraordinary and disproportionate amount of work to make them reliable, beautiful pinballs.

Unless it's Kiss.

You can sell Kiss for $7000.00+, so that is worth the time and effort.

Every other machine this age is a money pit of despair. (Not really...)

You can't come out ahead (if you actually do the things necessary to turn the machine into something that is reliable and beautiful) without investing too much time and effort relative to the sale price of the machine.

However, if you have a personal connection to a machine, or you know for certain that there is a person with a personal connection to the machine and would be willing to pay substantial money for a 'best restored in the world' example, that would be the exception.

If you love it, there is no price too high to pay.

If you are developing skills for other restoration projects, consider it like the cost of a semester in college. It'll pay off later, IF you choose the right job in the future that will actually make you money. If you choose to restore these machines over and over you might end up bankrupt.

(I'm looking at this from a retail business viewpoint! Of course, as a hobby you can do as you like, and every thing you do to keep old pinballs working is absolutely to the good of the hobby of pinball. I bow to you, for your efforts. Because of you, one more pinball that was 'lost' is now playable. Well done!)