Why are the landlord's costs going up "at the market rate" (which we will assume is higher than inflation)? Because the plumber lives in a market rent apartment and has to charge twice as much as a few years ago? Why would their insurance costs go up that fast? It's not like their property taxes are going up that fast. ;)

I believe the arguments that rent control is distortionary and poorly targeted (maybe they should make it means-tested rent control! I'm sure that won't have any effect on poorer people trying to rent! :P). But I don't see how market-rate rent increases, that happen fast enough for people to reach for rent control, are because the landlords are maintaining the same margins and seeing their costs increase. I do get the opportunity costs and reduced resale value costs though.