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The olimex company just announced the: RVPC - a kit PC with a RISC-V CPU, and they say it'll cost US$1
(olimex.wordpress.com)
This is a most excellent place for technology news and articles.
A CPU on its own cannot be a microcontroller alone via its definition; as a microcontroller contains a CPU and other needed components to drive it.
No microcontroller is going to beat a computer with a modern microprocessor on complex computing though. But it's good to know tech is still improving on all sides.