There is a sense in which you only get a shortage as a result of something like price controls. If Saudi Arabia stops producing oil, the price goes up, but you can still get it. But if the government institutes price controls then people buy all they like at that price until the supply runs out. Then you can't buy it at all because nobody who has it wants to sell it for less than the price cap and nobody is allowed to sell it for more.

There is another definition of a shortage which basically says that supply doesn't respond to price, i.e. even if people are willing to pay more, the total amount of supply doesn't increase.

If gasoline was suddenly $50/gallon, it wouldn't stay there very long because it would immediately be profitable for new supply to come online, using production methods that aren't economical at lower prices. Supply would increase in response to higher prices.

This is also true of COBOL developers. If they were highly paid (relative to other software developers) then more people would learn COBOL and the supply of COBOL developers would increase in response to the high price.

It isn't really true of housing in SF. The price goes up and the supply remains the same because new construction is constrained by zoning. So there's a shortage.