I part out between 35 and 50 machines a year but I would never part machines out that could be saved. I have what I call the two out of three rule. I see a pinball machine as three major parts: backglass, playfield & cabinet. For me to part a machine out two out of the three need to be beyond being able to be used. ALL machines are worth more in parts but I could never part a machine out that was worth saving.
About 3 years ago I realized I just had too many so-so machines sitting around so I offered them for sale. Once all the better stuff sold I started trying to figure out what to do with the rest. And that was when I realized machine with two out of three bad are never going to sell. So I decided to help other machine live on by making "junk" into parts.
After I had been at it for a while local pinball guys started contacting me with their "junk" - partway striped playfields, nasty machines that had been sitting outside or in barns, etc. and when they learned I would buy them it all began. Three years later I am parting a machine out about every week to 10 days.
Being very honest I don't do it for the money because once I buy machines, pay storage rent, pay selling fees, etc I don't make a lot per hour doing it. But I hate to see good parts just sitting or ending up in landfills so I feel as though in a way I am helping some pinball machines live on. Yesterday I saved 3 that were headed to the dump later this week and after dealing with the nastiest mold you have ever seen I am thinking maybe these 3 were not such a good idea. But I did still savage a ton of good parts from them.
Anyway - anyone that has machines worth restoring PLEASE do not part them out. It happens way to much and it is sad to see machines that could be saved become parts.