The joke with the Raspberry Pi is that it is 1) so cheap because its manufactured on an old silicon node but of course that implies 2) it actually uses a ton of power compared to a chip made in 7nm.

From what I could find the RPi chips are made in 27nm, and while you can't exactly linearly extrapolate from that, I wouldn't be surprised to find that a 7nm smartphone chip can get you the same performance as the RPi at 1/3rd the power consumption.