Housing costs are high because it's hard to build a house. It's a dangerous task requiring a lot of logistics and coordination. There are toxic chemicals, dangerous heights, sharp objects, and requires being in unhealthy poses and breathing in fumes during the construction. Then there's the financial risks, with people not paying as promised, or withholding some pay due to work quality. At the end of the day, people are not willing to sacrifice their health as cheaply, and there isn't a new influx of cheap migrant labor, so the costs will remain high in the future.