[nine_k]

British customs used to have a simple mechanism to bind declared value to market value.

A captain could declare the value of the cargo whatever he sees fit, and pay the tax on that amount.

The customs reserved the right to buy the entire cargo at the declared price, at their discretion.

It's a bit harder to implement with large parcels of land, but should work well with home-sized lots.

[andreareina]

This works for cargo because much of the point of cargo is to sell it. The point of a house is to reduce the buyer's risk against e.g. rent going up. Except now there's the risk of my house being bought out from under me unless I'm willing to pay above-market tax. Money is fungible, housing really isn't.