A generic 12v 20a power supply that s19 pro needs costs a mere $60 where i live.
The miner does not use a generic 12v PSU and what they use delivers a lot more than 20A. 12v*20a=240w so not even close to the over 3kw the s19 pulls. Modern miners use variable output PSU's that adjust the voltage to between 15-20vdc at well over 150amps.