Not sure I saw any claims in this thread about its cost before yours but open concept IS cheaper to renovate. Adding walls, plumbing, electrical where there aren't any is much easier and cheaper than removing walls especially since you often need to re-route various services or loads.
Really? Because I see it all the time. "This house gives us the option of finishing a basement or adding a bedroom." "This house gives us the option to add a garage." "This house gives us the option of moving a mother-in-law in or expanding our family more."
For
you maybe. Not all of us have so much crap that we have issues with storage in our open concept houses and not everyone needs every room to be private. Dust seems to be an odd thing to mention. How do you figure that? If we take two otherwise identical houses and one is open concept but the other isn't your total dust gathering surface area is roughly the same but open concept has fewer hard to clean\dust areas.
Open concepts are not what has driven the demand for increased footprints. Open Concept is a relatively new trend while the average footprint already doubled between 1950 and the early 00s. The increase has basically been linear since 1980 or so so the effect of it on overall footprint is minimal to nonexistent.
https://www.census.gov/construction/chars/pdf/squarefeet.pdf
Open concept does not affect HVAC\door\plumbing requirements. Volume and envelope size does. While Open Concept and high\vaulted ceilings are often used together high\vaulted ceilings are not a requirement for open concept (although its a somewhat vague term)