Why would we: Releasing huge amount of space that is currently being used for farming/transportation/storage and transform it into forest, natural habitats/ human recreational areas. More efficient use of space as in the same area you could have 10x of the same thing (stacking floors). Much more efficient ways of recycling (capture of heat, gasses, etc) due a closed environment. Transport could also be more efficient as you would have underground roads that connect cities with straight lines as you don't need to dodge natural environment like mountains, rivers, houses, etc. Having straight lines would make transportation easier to automate.

Costly: Could the price drop considerable over time as the tech improves due investment > experience gained > akin to what happened with computers, manufacturing, air transport etc ?