Given that land and the like is a limiting factor, the only way to get it cheaper is to develop the middle of the US (assuming it's about the US anyway), and / or to go upwards.

But that too has limits; megacities like Singapore have built upwards for decades and is still one of the most expensive places to live.

And another factor is that landlords and investors will resist oversupply. This is where China went wrong, billions have been invested in brand new cities that are effectively ghost towns; preparing for an influx of people that never came.