(I speak as someone who sucks at programming and doesn't spend a 1/100th of the time learning the latest as I used too as a teen. So having the community around to help with my latest project that I need something more than a microcontroller for, is immensely worthwhile. Obviously those who don't need these types of spillovers would probably be better served with other hardware.)
I mentioned it above, but just to reiterate- there are lots of great hardware boards out there and many beat the Pi (though the 4 makes up the different finally). However, they ALL have terrible software support: old OS's, bad drivers, out of date or incomplete documentation.
The Pi community makes it worth it to stay there.
Then you should also compare the Chrombooks with second hand large format laptops, old servers on sale with new ones and so on.
Chromebooks 'on sale' are an entirely different class of product than raspberry pi's, they are larger, need wall power, have built in batteries and screens, are in general still more expensive and do not have GPIO.
RPis pretty much never go on sale.
Pretty much everything works on the existing rpi. Heck you can run Windows IoT on it. It has a UEFI firmware (edk2) port which mostly complete, and pretty much every distro and 3rd party OS supports it. And the hardware itself is mostly open at this point.
If you're doing stuff that needs the Jetson, it's great, but the Pi is definitely better supported.
A57 and A72 are very close in performance, as the A72 is an evolution of the A57. ARM's numbers have the A72 around 20-30% faster than the A57. The main advantage of the A72 was it fixed the horrific power problems the A57 had so in a phone usage you could actually use the CPU for longer than 10 seconds. But in raw performance it wasn't that much of a jump. A53 to A72 is around 2-3x as fast, though. A53 was the power efficient one. A57 was the performance one.
Both the Jetson Nano & Pi4 are clocked at around 1.5ghz, so the Pi4 should still eek out a bit of a CPU performance gap over the Nano. But if you're purely comparing factory vs. factory then the Nano would probably win over longer stretches as the Pi4's lack of heatsink results in it throttling down to around 1ghz after a few minutes. The Nano looks like it has a beefy enough heatsink to keep the A57's churning for a lot longer at their 1.43ghz spec.