Comment by noobermin
I guess I'm old because this hasn't really been that insightful of interesting observation just by itself anymore. People often talk about technological advancement of computing as if it is a force of nature whereas the amazing specs of say a rp2350 compared to the cray-1 is more of a story of the economies of scale as opposed to merely technical know-how and design. The reason a rp2350 is a few dollars is because of fabs, infrastructure, and institutional knowledge that likely dwarf the cost of producing a cray-1. I wouldn't even be surprised if someone bothered to do a similar calculation of the cost of infrastructure needed behind each cray-1 at the time that it could even be less what is needed to produce rp2350s today. The unit price of a rp2350 to consumers being so cheap (right now that fabs still want to make it) somewhat elides the actual costs involved.
Animats below said that the Cray-1 was made from discrete components. Good luck making a rp2350 from discrete components, it likely wouldn't even function well at the desired frequency due to speed of light and RF interference issues--it would likely be even worse for GHz broadcoms used in the rpi5. This means that in a post-apocolyptic future you could make another cray-1 given enough time and resources. In 20 years when the fabs have stopped making rp2350s there simply will not be any more of them.
I think the really interesting post here is that a reasonably high level of computer is basically free. you can get a 32 but microcontroller with 16mb of ram at above 100mhz for well under $1. you can buy a USB cable and it has 2 full computers inside it.