I think the reasons why rent can beat ownership on costs are multifaceted but may include factors like:

• If all or most of the landlords in an area already own their property outright, they aren’t paying for mortgage interest. Then, in a market with demand and competition at a certain level, prices fall to a an equilibrium that goes below the cost to finance and own that property as a new buyer.
• Larger buildings probably favor a large single owner for total cost as a rule. A condo building is like all these individual owners getting individual financing at retail rates for pieces of a building, then having to pay maintenance on top of that. A property developer is getting a much different type of financing.
• Businesses can deduct costs in ways individuals can’t and have an overall lower tax burden.
• Large landlords can hire maintenance staff full time and spread them around their buildings to pay a lower rate and cut out middlemen.
• Large landlords can buy renovation materials and appliances in bulk. My last landlord had the same cabinets and appliances in every single property across town.
• Single family homes are probably less efficient to service and rent out and that’s a large chunk of the overall housing market in buyer friendly mid-size markets compared to large cities. Only recently has the real estate investment market started getting into mass ownership of single family homes.

The New York Times rent/buy calculator is a wonderful tool for figuring out whether a rental or home purchase is the best choice in your market.