There's a different limited supply: the paychecks of the potential renters. Can't extract blood from a stone, but they can try to squeeze it right up to the lim

There's a different limited supply: the paychecks of the potential renters. Can't extract blood from a stone, but they can try to squeeze it right up to the limit. People can only live so far from their jobs before it's no longer worth any savings in rent.