3 is tens of megahertz of one CPU core per re-encode, clearly out of the question with todays norm being ~ 4GHz 8 core CPUs, that or they are spyi^^^ recording everything for 'metrics/analytics'.
CPU time is irrelevant for re-encoding due to bandwidth reasons though. If a client requests 64kbps voice, sending it packets at 128kbps and letting it re-encode once it has them is pointless.