Such development boards are a completeley different thing compared to RVA23-profile RISC-V CPUs.

This is like comparing an 48MHz ARM-Cortex-M0 with the CPU in your Macbook. Yes both of them are ARM cores, but the small embedded processor has very little RAM/Flash/clockspeed, no memory management unit, no cache, no modern RAM interface.

Not even the instruction set is really the same, because you (typically) won't even have floating point instructions/registers on the small MCUs, much less vector instructions.

The Milk-V Jupiter 2 mentioned in the post is basically a full-fledged Desktop CPU and it's price is not gonna be anywhere close to $2 either...