There is so much wrong with your argument here I don't even know where to start.
Credibility out the door first as soon as you mention e-waste. I'm so tired of this argument. There is absolutely no reason any Mac (or PC for that matter) should wind up in landfill. Apple will take an Apple product, of any age, and many other companies' products, and recycle it for you, for free. For recent enough gear you can trade it in for money. And they'll repurpose or recycle the old one. E-waste is a straw-clutching argument.
Next you're trying to make comparisons between today's Mac Pro and 20 years old PowerMac G4's??! Ok, you're still using them for file servers? Serving what kinds of files to where? The newest MacOS a G4 can run is leopard. The security holes in that OS today, alone, are a major risk. The maintenance overhead on anything that old (hardware and software) to keep them (a) running, and (b) compatible with anything else your network needs must be problematic. What do you do when an ethernet port or logic board fails? ie. What does that cost in hardware repairs? And what does it cost in downtime also?
All power to you if that's what works for you but one of two things go from there: whatever time you're spending on maintaining those older machines is either...
(a) saving you more money than you make doing whatever you do for a living with these machines, in which case a Mac Pro isn't going to make you any more money than a Mac mini would and it's not financially sensible for you to justify being in the market for a Mac Pro anyway. Or...
(b) you'd make more money with the time spent maintaining that stuff if you spent it doing the work that makes your living with these tools, and you'd be better off making that money with your work and spending it on better hardware so you didn't have to maintain the old hardware (and software).
A brand new $800 Mac mini would easily replace multiple Power Mac G4s (you can't put more than 2GB in a PMG4, and it won't run anything better than leopard). Let's say you make $100 an hour. You can't tell me you're spending less than 8 hours per year maintaining those machines, or that a logic board or ethernet port or anything else hasn't blown in all the time you've had them.
What you're doing is perfectly ok if that's what you enjoy, but comparing that description to the work of anyone even remotely in the market for a Mac Pro is the part that's ludicrous.
A Mac Pro is supposed to be a high end business tool for people who generally make a lot of money using it. Artists, film makers, sound engineers, developers, maybe lawyers, & accountants, and any number of other professions where time is money time spent waiting for a slow computer means money lost. When a company or self employed individual could make $300 per hour from someone using a tool and the tool slows them down so that they can only deliver $200 an hour's worth (and therefore only charge that much), then it's very affordable to buy a better machine. It's got nothing to do with being rich or poor. If the expensive machine doesn't save you enough time such that you're not losing money for that lost time then what do you need the expensive machine for? It's not worth it and you should buy a cheaper computer to make the expense worth it.
And if your needs only warrant a cheaper computer then replacing it with another cheaper computer when its usefulness runs out is also affordable. It's simple economics.
I've got nothing against the idea that if a computer has upgradeable RAM then great, we can make use of that. But get your head out of your a... Tim Cook isn't soldering RAM to the inside of the SoC because he's a greedy bean counter. He's doing it because it makes the product better. Why should Apple cater to tinkerers at the cost of performance?
That $10K-$20K you mention is NOT $10K-$20K Painting that picture is a deception. Upgrading a modern Mac is easy. They hold their value better than any other PCs. You sell the old one, and buy a new one. That exercise doesn't cost $10K. For a $10K computer it might cost $2-3K. Whatever it is, let's call it $X.
In comparison, perhaps upgrading RAM in an existing computer costs $Y. And the kind of RAM that goes in a $10K computer is not cheap.
The cost of non-upgradeable RAM is not $X. It's the difference: $X - $Y = $Z. And $Z is usually not very much, especially when for $Z you get a new processor, storage, and all the other upgrades that also help improve the performance of the machine, which will (a) make you more money because you get your work done faster (if you're a professional who relies on the tool to get your job done, and if you're not then you don't need a $10K computer in the first place), and (b) also make it worth more to sell when it comes time to replace that. Not to mention a new warranty that means the cost to repair anything that goes wrong is zero, and a newer computer is less likely to break down meaning the cost of loss of usage is also less. The cost of downtime is not zero.
It's all well and good to want to upgrade the RAM in your Mac, but you people continually pushing this idea that Apple is greedy and insane because they don't let you do it any more (and trying to use arguments like the above to push that) ... that's what's ludicrous here.
Once Apple Silicon was done, that’s it, one hit, everything else is just iterations on that. They only need to compete against the most recently released Apple Silicon chips as there’s no other vendor making macOS computers. As long as the next MBAir is faster than the current MBAir, that’s 80-90 percent of their potential Mac customers right there. Anyone needing a 96 core x86 system won’t find anything to like about a a non-96 core, non-x86 system. Apple doesn’t do x86 anymore so Intel and AMD have that entire market to themselves.
