A lot of money in Pinball IS markup. A Mfg may get clear posts for 10 cents a piece in bulk. But if you try to buy them at even a Pinball show, at a reduced price... you get charged like 1$ per post. That 90% markup, makes it hard just to afford to repair machines... let alone make one from scratch.
Ive seen wire harnesses being made. A lot of the cost is in the initial time spent in designing and building the custom loom. Once thats made, its pretty much run the wires, and cut.
The real labor starts when you have to solder 600 connections. As well as put in 600 screwed in posts, screws, nuts, etc. They have some things to help, such as air powered drivers, plenty of space and organization, etc.
The problem is that Stern isnt interested in remakes. Nor is it effective / efficient for them to do small runs.
A game like "Flying Turns" ,would be a great starting project. A simple EM machine.. but using a new electronic PCB instead to drive it. Flying Turns looks simple, but its actually very fun.. and can teach a person much more about playing Pinball.. as you Need to 'bump' well, in order to survive, and thrive.
Its also infinitely more fun than any Virtual Pinball game.