Yea it seems unrealistic. I imagine many people buying a home at $N would prefer to upgrade finishings or increase the size of the dwelling, or put in a tennis

Yea it seems unrealistic. I imagine many people buying a home at $N would prefer to upgrade finishings or increase the size of the dwelling, or put in a tennis court than to actually pay less than $N. You can almost indefinitely add marble counter tops or antique bricks to increase the cost of a home. This luxury side of the market is actually considerable.