I think what you guys are trying to do is not possible. In the neighbourhoods you are talking of, it is not first time buyer territory, even if some are. Buyers will have wealth from earlier years and from other sources I don’t think you can statistically calculate the buying power of the typical purchaser in excellent neghbourhoods. All you can do is observe developments and use overall earning and employment data such as that used by Rich to assess trends. there may be less frequent income /wealth decile distribution data which can show you how the rich get richer which could also be used.

But some area will always have a significant number of non-typical people and I would imagine the nearer you get to the coast the greater the percentage of buyers who don’t even need a mortgage.