It’s untrue. Unstated assumptions are the quality of housing desired and location desired. In practice, because of the rent/price ratio being low here in SF mos

It’s untrue. Unstated assumptions are the quality of housing desired and location desired. In practice, because of the rent/price ratio being low here in SF most people will be taking a downgrade when going from rent to 1.25x that as mortgage after putting down $300k for a $1.5m. It is true that the marginal rate can be very high, though, so heuristics based on pre tax income break down at these numbers. The place we live in costs $7k/mo but to buy it we’d have to spend $450k and then $9.5k/mo.