The wealth is the ability to live in a desirable place, that is structured so not many others can live there. You could mess with the accounting or the liquidity, but it is still wealth that few people have and most people don't. In fact most such real estate multimillionaires are not interested in cashing out. Only in continuing to live there, and making sure that not too many other people start to live there. Liquidity is worth something so it would reduce the price somewhat, but I don't think it's central.