People live here and would like to build a life for themselves instead of living with roommates into their 40s and 50s.
You could feasibly quadruple the population if you wanted to, I guess my question is to why? It wouldn't decrease rent appreciably, and you would have to move out to daly city to raise your family in something other than an apartment.
You could do all this building and ruin the atmosphere of the lower half of the city just for Amazon, Salesforce and whatever other software companies are still downtown to move to some desert and have the rents drop back down to normal ranges.
You live in a fantasy world if you don't think increasing the housing supply by 4x will do anything to prices. Austin is a near-perfect natural experiment... not that you likely care about good-faith discussion with a month old throwaway account.