Opportunity cost is the loss of potential gains from other choices <i>when you make a decision</i>. It is <i>not</i> the theoretical amount you&#x27;re pissed off about &quot;losing&quot; but for the existence of a law you don&#x27;t happen to like.<p>People who owned property with a certificate of occupancy prior to June 13, 1979 (i.e. a rent-controlled property in SF) can genuinely grouse that they bought an asset with a different expectation of return than what they got. Everyone else bought into a system knowing the rules of the game. It&#x27;s no more &quot;opportunity cost&quot; than someone who buys a suburban property with land-use restrictions complaining that the laws prevent him from using his land to start a refinery.<p>If you buy a rent-controlled building today, you know that you&#x27;re buying a building with a defined revenue stream. It is not &quot;opportunity cost&quot;, except in the sense that you chose to buy the building in the first place.