A world where most housing becomes disposable (i.e. it is not directly tied to the land it sits on) would be very different from the one we currently live in.
In any case, at least for building straight up, there is scope for improvement even with the land remaining a bottleneck.
The general rule of thumb is $100-200 a square foot for houses so a fairly typical 2,000 square foot house is going to probably cost in the neighborhood of $300K to build. That assumes the land has water, electricity, sewer/septic, etc.
So for fairly typical exurb/suburban locations (i.e. not Bay area, Manhattan, or back of beyond), the house and the land are probably roughly the same value.
So basically the trailer park model?
[edit:] yep, https://news.ycombinator.com/item?id=10303455