But isn't this exactly what we'd expect? You can't have everyone able to afford housing that is in the top 50% of housing costs (except possibly in Lake Wobegon).
This seems like the housing equivalent of those periodic "richest N% have M% of the wealth" where M > N stories that present that as something obviously bad when in fact in any population where there are variations in wealth it is mathematically necessary that the top N% has more than N% of the wealth.