I don't think that's a big problem TBH. In July, I overpaid for a Fish Tales (it was £3k without topper) as a first pinball machine, we're having massive fun with it, and I've just bought a LoTR.
In total, we've spent less on those two pins than a new Godzilla.
So, it's not like you can't get involved in the hobby of pinball unless you buy a NIB Stern
Honestly, whilst I agree that you don't need to buy a NIB machine to get into the hobby, I do think this will be a problem down the line.
There are a finite number of the older machines floating around, and they've been increasing in price for as long as I can remember. Simple supply and demand - as more people get into the hobby the demand increases whilst the supply stays the same, hence the price increases on older games.
Then there's the fact that people are reluctant to let games go because they know they'd have to buy them back for more if they want them again in the future = less supply.
This ties into NIB games because one of the biggest motivators for most of us to sell a machine is wanting something new and shiny - we're all restricted to some degree by either space or money. Neither are infinite. So if the prices of NIB rise so high that most people are priced out or just unwilling to pay, there's less new games being bought which equals less older games being sold, further supressing supply.
And on top of all this, it means less titles available on the secondary market in the future. Using LOTR as an example - that would have been NIB in around 2004 for around £4k or less. It was a popular game, and at that price quite a lot would have been sold NIB, hence there are quite a number of them around and they frequently come up for sale. With machines selling for £10-12k less are bought NIB which means less supply in the future than older games.
When I got into the hobby 17 or 18 years ago a Fish Tales could be had for well under a grand, along with many other 90s titles. Our first machine was a really nice Twilight Zone which I think cost us around £1.4k. For the £3k you spent on Fish Tales someone new coming into the hobby could have bought 4-5 machines. So we've already priced out people who don't have at least a couple of grand to drop on a toy.
Prices only seem to be going in one direction at increasing speed.
Edit: Dug out an old post I made and updated it - these are the NIB machines I've bought and prices paid over the past nine years:
November 2012 - AC/DC Premium - £5995
April 2013 - Metallica MOP LE - £6695
June 2014 - Iron Man Vault - £4600
May 2016 - The Big Lebowski - €7550
September 2016 - Ghostbusters Premium - £7000
April 2018 - Total Nuclear Annihilation - Approx £7k (Bought direct from Spooky in $, Phil helped ship it over, can't be bothered to work it out)
March 2019 - JJP POTC - £9495
October 2019 - Jurassic Park LE - £9900
October 2020 - Stranger Things Premium - £8750
March 2021 - Rick and Morty - £7740
Clear trend there if you ignore Spooky games.
So looking at Godzilla pricing - since Nov 2012 a Premium has increased by 66% and since April 2013 an LE has increased by 79%!
One way or another, price increases like that are going to have an impact on people getting into the hobby. It would be like if suddenly every car produced cost over £50k - sure, in the short term people would buy older cars second hand, but the pricing of the new will eventually increase the pricing of the old.