While there is a huge benefit in running as much computation as possible out of the CPU and on more specialized chips, the two leading high end consoles use x86 CPUs to run a fairly large part of the overall processing. ARM is no magic and its price advantage came mostly from being simple and good enough at a time even the lowest end x86 would be overkill. Today there are some very low power x86 solutions that can compete with ARM solutions in both price and processing/watt.