I'm not sure if this logic works. Because you have to pay for both space and access. If you're able to buy a McMansion in a dense city, that's because you valued this particular combination of access and space more than anyone else; and in fact, you were able to outbid a developer that could have built an apartment complex on the spot.

I'm not convinced that urban sprawl is a result of free market forces giving rise to a Tragedy of the Commons. It seems equally plausible that urban sprawl is the result of government intervention: zoning laws that restrict density and promote single family homes, usually voted in by incumbents who want to preserve "neighborhood character". But the market value of these plots of land may actually be higher if they were allowed to be built more densely.