Why though actually can't we build the way our ancestors did? Is that knowledge all lost? The Palace of Westminster isn't a farmhouse but it seems like a pretty beautiful, functional, durable building.
It does not cost a million dollars to build a single detached house. Closer to a quarter million for materials and labour, give or take the cost of land. Profit for the seller is what makes up bulk of the cost. Profit margin for the builder. Decades of steady profit for the bank that sells and services the loan. The purpose of housing has become to be an investment vehicle, not shelter.
We could easily afford to build and maintain enough housing for everyone. Create and sustain vibrant communities where people's basic need of shelter are met. But it's just not compatible with the capitalist mindset.