https://www.newegg.com/amd-ryzen-5-5600-ryzen-5-5000-series/... $150
https://www.newegg.com/p/pl?N=100007709%20601394871&Order=1 starts at $210 indeed.
People might argue the 5600 is Zen 3 where the 8700G is Zen 4.
And 8500G is $176 also with stock cooler.
At least if the infos in this interview with someone from AMD hold up until marked release: https://www.youtube.com/watch?v=GNrOY9YCRSs (2min in)
the 8600G seem to be $229 instead of $299, which seem to have been a mistake of the interviewer in the video
the 8500G seem to be $179 instead of $176 which was a typo on my side
Like OP mentioned they have only 8 and 4 CUs respectively.
In comparison the Steam Deck has 8 (RDNA2) CUs, so while you can't really call a 8600G a "desktop gaming" APU it still can somewhat run a lot of games, enough for many very causal gamers.
For comparison the minimal GPUs in the 7x00X CPUs have 2 (RDNA2) CUs, which is still enough for most office PCs and still can run stuff like Dead Cell on 1080p reasonable well. Now Dead Cell is highly optimized but what I'm trying to say is: If you get yourself a cheap office PC or update of one and want to sometimes play some simpler older games a 8500G can still be all you need.
That combination uses more than a little extra power, relative to the APU.
The dGPUs have more cores and wider memory buses/dedicated memory which delivers higher performance than the space constrained integrated GPUs.