Would the Conservatives' plan make new houses 50,000 cheaper?

Conservative shadow chancellor Andrew Griffith has said his party, if it was returned to power, would take £50,000 off the cost of building a new home in England and Wales by cutting back on regulations. The £50,000 figure claimed by Griffith reflects estimates by the housebuilding industry of the costs of new regulations and taxes. However, construction and housing experts warn that some of the savings could ultimately lead to higher government spending on schools, roads, and affordable housing. And some analysts also warn the Conservative plans to scrap environmental regulations could potentially push up household energy bills in future. Where does the £50,000 figure come from?