Someone has to do this, eventually electronics hardware prototyping has to stop lagging behind several decades.
Your argument doesn’t pass a self-integrity check. You can get boards for a few tens of dollars. You won’t get them today.
You can get boards tomorrow, or if you happen to be close to a fab and submit your order before lunch maybe same-day. This doesn’t cost tens of dollars.
So simplify: mill instead of etching, which also handles drilling. This needs 3-axis movement, which is all you need to drop solder paste on pads and do pick and place too, you just need a tool changer for each task. Not a trivial project either, but it's been done and certainly not for an absolute fortune.
Final step is reflow soldering, and this can be done using just a heated plate [1]. This all seems doable for most hobby sized PCBs.
People are doing this today but everything is jank, nobody's repackaged it with prusa-like reliability at hobbyist prices AFAIK.
Ideally if you could get v thin copperclad with a substrate that doesn't produce toxic dust, with the right software and jigs you could produce "basic" multilayer boards(1) with 1 "pin aligned" flip and a few manual tool changes for drilling etc.
It all seems possible today but has never been packaged nicely and made cheap, I suspect because the market is not big enough.
(1) one big issue... the boards produced would be vastly inferior to "real" multilayer boards, would mainly be usable at low frequency, you could get complex layout / routing but they'd suck at high frequency and in several other ways. You would need to relayout / redesign to target a "real" process, which is somewhat undesirable for prototyping.
A soft goods shop I know bought everything they need to do prototypes in house. Now they can crush everyone else on delivery schedules and are fully self-determined and therefore also more reliable on those timelines than anyone else. Those two things together draw very lucrative projects.
Imagine if you could do the same thing with electronics, moving prototyping entirely in-house and modifying the workflow to match. It would create an entirely new class of shop, and I would bet a lot of interesting changes would flow from that.
They can pretty much do that now. But nobody has a nice solution for thru-holes yet. And single sided boards are pretty boring.
how else would all those billions in R&D would be worthwhile for investment institutions?
as I see it (and stretching my reasoning), the lag is also part of what maintains the prestige of many academic and research organizations.
the billions in R&D are not all about the outcomes, a lot of them are spent making sure it's really damn hard for any rivals to catch up. how exactly? I cannot know but I can infer it's got a lot to do with having nobody able to see the whole picture, anybody can only know either how to design the chips, xor how to build them.
if everybody is as good as MIT, then MIT is no longer MIT. somebody has got to make sure some of those 3rd party (and far away) institutions stay there, in the back.
if everybody could do "2nm" process (whatever that means), then TSMC wouldn't be ahead of Intel, and so on...