If there is a greater demand for units than supply, price is set by the top N buyers. If you boost everyone's spending power above that price without increasing

If there is a greater demand for units than supply, price is set by the top N buyers. If you boost everyone's spending power above that price without increasing supply, market forces will tend to raise the price until it's affordable only to the top N again. In housing, this means that you can boost people's spending power to help them afford rent, but you also need to build more units or you're just going to fuck everything up.