This house is 375 sq ft and uses low end materials, and it doesn't include setup, so it's going to cost ~$100k, or $266 / sq ft. Most new home construction is more like $150 / sq ft. And with this system, you're very limited in what you can build. Who's the target customer for this?
The construction prices you quoted are not correct at least in the Bay Area. And I am guessing $150/sq ft achievable at scale. Pricing ADUs is tricky because the some of things in a house cost same for a small to medium size home. For example, the costs of plumbing, electrical, kitchen, bathroom, etc are more of less the same between a 500 sq.ft. house and a 1000 sq. ft house.
Don't larger houses have multiple bathrooms, thus not the same cost for plumbing? At least when I watched Selling sunset, it seemed it's about having at least 3-4 bedrooms and 4 bathrooms in a house...