> It costs pretty much the same to live in a tin shack with no running water or electricity and eat rice and beans for every meal everywhere.
No it doesn't. First of all, the price of land can vary wildly. One square meter in the middle of Amsterdam will be a bit more than a square meter in Bumfuck, Alabama. IF you can buy land at all, in some places you can only lease it (you could own a home, but not the ground it sits on). Then there's all kinds of taxes you'd have to pay, just for owning that piece of land.
A 19.5ft by 8ft parking spot in London was on the market a few years back for £350,000, and you won't even be allowed to build a shed on it, just park your car.
An empty lot without even a tin shack can cost more than a mansion, depending on location.