Where do people get these idiotic ideas? Say it's worth $5 (to you), won't you?
It's really easy to check the data: PS5: RDNA 2, 36 CUs, up to 2.23 GHz, up to 10.28 TFLOPS PS5 Pro: RDNA 2(+), 60 CUs, up to 2.35 GHz, up to 18.05 TFLOPS Steam Machine: RDNA 3, 28 CUs, up to 2.45 GHz (if what they say is the boost clock), up to 17.56 TFLOPS
So no, not half the CUs, definitely not half the performance, not rebranded 6600 as this is RDNA 3, and even if it has less theoretical maximum compute than PS5 Pro it will have better utilization and probably 32 MB Infinity Cache. This is slightly higher clocked, higher TDP 7600M with much better cooling. The CPU looks like, at worst, 8540U/Z1 with better TDP and much better cooling and being Zen 4 its 6 cores should be better for gaming than PS5's 8 Zen 2 cores.
Valve has supplied one of the most detailed explanations yet regarding the Steam Machine price. After a Skill Up interview, gamers know that the company will not absorb losses to compete with Sony. While a comparable gaming PC would cost more than a PS5, Valve believes its system has console perks.