Why do people keep ascribing high housing costs to some nebulous "greed"? Isn't all economic activity due to greed? Anyone trying to choose a lower priced thing to buy or trying to get paid a higher wage is also doing it because of greed.

The parent is right. Shanty towns are the extreme low-regulation end of housing and they're also extremely cheap. It's a matter of how bad we want to allow people to treat themselves and our standards for safety and comfort keep going up so cost does too.