Realistically unlike older machines modern machines have been further redesigned to be comparative to "throw away pinballs".

It is still easier to find game specific parts for games built between 1977-1985 than a Stern game built in 2000.

There are plenty of examples.
The next generation is accelerating further with Stern's "The Pin" 2.0.

Many EMs and woodrails are built like tanks in comparison to most modern games.

The cabinets have been the comparative since the late 1930s, with the exception of cabinets made in 1980s during the video game era (particle board). Once upon a time most cabinets were painted or silk screened. Granted there were exceptions, but some know how those turned out in the long run. Glue delamination happens faster than the past, and construction quality has decreased including using particle board bottoms. Hell even AGC cabinets are better construction quality than modern games, even with paint flaking problem.

Playfield production has remained consistent in standards since the late 1940s, only the hard coatings have changed. The equipment to make them was produced after the Second World War, which as someone pointed out companies like GTB DID make parts to support the war out of directive and necessity.

What has changed are the quality of other components, especially metals and wiring, not necessarily the SS electronics. Connectors for games have continued to get cheaper and poor quality, that is why edge and IDC connectors and associated non coated pins were used for a very long time, and why they burn and fail.

It good to see that some people are finally realizing that the cost saving measures being utilized today result in many games being thrown in the trash in less than 20 years. People are spending a LOT of money on crappy non-bulletproofed games because they do not know what GOOD looks like. The first time they buy an older game prior to 1984, some get surprised at the difference in construction.
It is not insignificant.
I spent nearly 100 hours, "bulletproofing" my MET PR to fix potential pitfalls and problems.
This had nothing to do with the PCBs.

Stern has for example moved toward a ensuring that modern parts are not available for even titles made in the past five years, or made the parts so monopolistically expensive that it forces operators to buy new games.

For many new collectors, they simply do not care, as they will not be around to care in the short time anyway. That is the honest direct truth. There are reasons why dealers do not like to work on specific manufacturers past certain periods of time, not exclusive to lack of parts, but also experience, or simply lack of profit.

Anyone that owns a IPB BBB will know the extremely level of quality they provided in building this game which eclipsed anything that Capcom provided at their factory. IPB even put BLY/WMS to shame in terms of their construction.

Times continue to change.

Cost of NIB games have NOT "marginally outpaced economy inflation".
Those that believe this are uninformed, do not wish to believe, or as I stated just don't care.

Know what you are buying for "$10,000", it is not a classic motorcyle sorry to say.
If I was, it would be a masterpiece.
It is all fun, until it starts to slowly (or rapidly) fall apart in front of a person's eyes.

Compare a part for any GAME SPECIFIC Stern game made in the last five years.
This includes lock bars.
I am not talking about the generic powdercoated black lockbar with tournament button hole plug used in the 2000s.
Prices are 150-200% higher.
Some game specific parts from the factory are over 350% production cost.
They are not going to get any cheaper as they disappear.

Don't expect Stern to loosen their grip for reproduction either.
If someone loves their "holy grail" pinball machine they had better go through a distributor (lower price) and buy that stock part now.
It 10 years in will be "unobtainium" more than any BLY/WMS part today.

That is why some willing be making "big money" in home repairs in the next 5-10 years.
I look forward to the change of times again as the market reshifts once again, either for repair or purchase.
There simply are not that many people who really understand how to tech machines from 1955-2015, and they number is not outpacing the number of collectors.

"A pinball machine that does not work is a 300 lb doorstop."