> hardware which is tons better

tons better at *what*? rp2350 is pretty darned good at being a microcontroller. i don't know if you've ever programmed an 8051 but i'm pretty happy to not have to very often.

from a power perspective, even though the rp parts aren't that efficient they absolutely smash the milk v duo SOCs.

i don't think anyone here can answer the cost question with any sort of authority.
but my 2c is that the total cost of any product is more than the cost of the components. a lot of engineering goes into designing a system, documenting it, testing it, writing software for it, answering customer questions.
How much of that does RP do vs Milk V? How much do you value knowing how the chip actually works, and knowing about all the errata?