A business is valuable to own if you think it may bring you more money in the future, or you think that owning it will give you an advantage over your competitors.
That's it. That's the entire thing. Nobody is trying to put a value on the relative social impact of Instagram vs the New York Times. Facebook merely calculated that they'll make more money as its owner than they would otherwise.
That our culture has seen to directly associate cash value with 'intrinsic' value is another issue entirely.