This month the medical office building at 45 N Ellsworth Ave put up a new sign at the entrances to its parking lot: "paid parking", rates posted digitally, the parking lot is monitored, $88 citation or a tow for anyone who parks without authorization.
The public can use the lot Monday through Friday from 5:30pm to 8am and all day on weekends. All other hours are limited to use by patients and tenants.
20 feet away on N Ellsworth Avenue, cars line the curb in both directions. The only posted restriction is street sweeping, 7-9am on the first and third Tuesday. But the restriction on this segment of N Ellsworth Ave is unenforced.
Anyone can park there for free, indefinitely. There is a city rule limiting a car to 72 hours in one spot, but nobody enforces it automatically (city webpage). A resident has to call the abandoned vehicle line, a city employee has to come out and document the car, and only then does the clock start.

One landlord prices and watches every space on their lot because it's their money. The city doesn't even bother to track it a few feet away.
It's not just this block. San Mateo's Residential Parking Permit Program (RPPP) lets residents in permit zones park on their street indefinitely, and the permit is free. Someone who doesn't live in an RPPP zone, or doesn't own a car, pays for that street the same as everyone else and gets none of the parking their neighbors get for nothing. Even downtown, where the city runs meters and garages, parking is free after 6pm and free again on Sundays.
San Mateo is asking voters this November to raise the sales tax and help close a $17 million budget shortfall.
A private landlord with a dozen spaces already worked out what those spaces are worth. San Mateo has thousands of them, and it has never charged for the identical parking sitting under those cars.