There's been quite a lot of dreaming in this thread!
Yes, we'd all love a 1+ GHz multi-core Linux-capable RISC-V SoC for $1. That's just not going to happen in the near future.
The Kendryte 210 is a good example of what's realistic, though I'm amazed they managed to get it as cheap as $8.
The SiFive FE310 (32 bit, 320 MHz, 16 KB SRAM, 16 KB iCache, some GPIOs/PWMs) is retailing through CrowdSupply for $5 each (actually $25 for a 5-pack). You can be sure CrowdSupply are making a tidy markup on those. And those are still being made on MPWs. If the FE310 was put into volume production on dedicated full-reticule masks with a good number of wafers made then it would certainly be well under $1, and possibly approaching $0.20 -- though I think $0.20 is getting close to the cost of merely packaging the die.
That's a kind of ballpark that a 20c SoC would be in from sipeed. You could get different peripherals in there (but not a lot *more* as pins are expensive), or a bit more RAM. 64 KB? Maybe, but to be honest, probably less than 16 KB, to make room for onboard flash.
Someone mentioned CH554 at 25c. Good grief! 14 KB of flash and 1.25 KB RAM. And an 8051 CPU which is awful to program by hand, and absolutely appalling code density if you use a C compiler -- at a guess that 14 KB flash would be as useful as 4 KB (8 KB, tops) on an ARM or RISC-V unless you have an army of code ninjas writing everything by hand.