[aaronm67]

You're comparing only the densest places (i.e. expensive places with mostly apartments) to only the least dense places, giant houses on big lots. Look at a pre-1950s / railroad neighborhood of basically any smaller/older city in the US, you'll often find a walkable, affordable neighborhood of single family homes.

Also - cheap land does not mean that it's cheap to build and maintain. Almost all of the infrastructure required to build (sewer, power, roads, etc) scale up with area, not density.