Most land is probably not terribly valuable except that which has some resources or is strategically located (e.g., Iraq, parts of Iran, Afghanistan, etc.) The land itself would be a giant money sink-hole with defense considerations and the like.
I good value proposition is the actual people themselves. If you can force them to work for you, and they are decent workers, that has a pretty good value. But one can get the best bang for the buck...err...gold or whatever...by leaving the land and all it's hassles to some puppet regime and buy infrastructure like water and power systems. The puppet regime can then force the people to use the utilities you own. They could make laws such that it is illegal to capture rain water and must buy all their water from the utility company for instance. And if you can arrange the right kind of regime, it can even enforce those laws.
I agree and disagree. Let me explain.
The value is really in genuine sovereignity and the possibility to utilise more than 50 years of economic and political knowledge. The people are valuable, no denying that. But it is the ability to put them into patterns of production and value creation that are not possible in today's mature democracies due to the effect of vested interests, that is really valuable.
There is no need to super-exploit anyone. There are intelligent, poor and hardworking people all around the world willing to work for what will be considered a pittance in the western nations. UAE, Bahrain, Qatar and Saudi Arabia essentially run on Indian and Phillipino labour. Imagine being able to give all these people a sphere where they can not only earn and remit, but also accumulate property.
Puppet regimes are unreliable. They can turn at a dime. When the person you have been bribing is gone and replaced by someone else, you have to begin the entire cycle of bribes again. Plus there are the profits of being in the governance industry. It's basically the difference between a legitimate business and illegitimate one.
There might be a market for things like the Pantheon. I would get a kick out of owning the thing, and I assume that more powerful people would as well. It probably could even be done in such a way that the Greek people continue to foot the bill for maintenance and such.
Sale of politically and culturally important landmarks is impossible. Some arbitrary vacant land which can be utilised to create a new country is actually easy in comparison. Plus, the parthenon's value is very limited, essentially down to the NPV of tourists ticket sales and from now to forever. It cannot be compared to the value of a new hong kong.