The "in theory" part is the assumption that laws will stay as they are. The "in practice" is that Bay Area development regulations are a one-way ratchet, where

The "in theory" part is the assumption that laws will stay as they are. The "in practice" is that Bay Area development regulations are a one-way ratchet, where more and more restrictions and costs are imposed over time. First something is proposed; then the government starts offering incentives for it; then it becomes mandatory; then it becomes stricter and stricter. Eg., take subsidized housing units ("inclusionary housing"). At first, the state offered an incentive to build them, through the state density bonus law. Then San Francisco made 15% subsidized units mandatory in 2002. Then it went up to 25% earlier this year. And now you can't even get the state density bonus, because San Francisco will just pretend it doesn't exist, and dare you to sue them if you bring it up.