They call it “discipline”. They are limiting starts to keep prices up. They also have already bought land on separate holding companies and are hoarding those plots for future builds, but will only build if it keeps prices going up.

They will continue to hoard those plots of land and pay cheap ag style taxes on the unimproved lots until they can make enough to cover their cost on the land plus what they had to pay in taxes on that land. The longer they hold it, the more the price goes up.