A 10k run can be a small run, if the development costs of the firmware is $1,000,000+ in which case the sw cost is > $100 / unit. A 10% change in development time would then represent $10/unit which may possibly be twice the price of the microcontroller...

Not all embedded equipment have trivial software. Quite a lot of products sets the customer price based on the know-how in the software, not based on the hardware cost.

And such know-how-based products are more likely to move between different hardware platforms which greatly affects the reason to have code in asm or in C.

I'm a bit scared when I see people putting forth too general claims. Arguing too general claims in one situation probably means arguing too general claims in other situations too. What I like about developing software is that most products are different. I don't have to implement the same wheel all the time, but have to figure out new "recommended" solutions for each and every product. In the end, my designs will have to contain more or less guesses depending on how much facts are known (even by the customer) and my own knowledge in the relevant area. But since I'm involved in the hardware and coding, the quality of the design will directly affect myself forming a feedback loop that makes sure I really do my best with the design.