> Thats super hard to value anyway, since without selling an item, you can't be sure what it would sell for.

Actually it's quite easy. For land, governments do it all the time:

* https://en.wikipedia.org/wiki/Land_value_tax

For many other type of property: what is the insured value?

Certainly not exact, but probably with-in an order of magnitude of accuracy, which may be 'good enough'.