This very ladder-pulling-up is written into law as rent controls. Although typically presented as a way to ensure that widows and orphans are not priced out by

This very ladder-pulling-up is written into law as rent controls. Although typically presented as a way to ensure that widows and orphans are not priced out by gentrification, rent control is actually a tax on 'people who have moved recently': landlords can and do get stuck with permanent tenants for decades who are now paying 20% of the market rate for their apartment, sometimes less than what it costs to even maintain the apartment. To compensate, they have to raise the rent as much as possible when a unit becomes available, to make up for the cost of carrying the far-below-market units with the permatenants. Anytime you move into or within San Francisco, you're subsidizing the people who haven't moved recently.