San Francisco's much-heralded "social justice" requirements for city contracts are costing local taxpayers millions of dollars a year in overcharges, according to workers in departments ranging from the Municipal Transportation Agency to the Department of Emergency Management. In one case, a Muni worker said the city paid $3,000 for a vehicle battery tray. Such parts can be found online for $12 to $300, depending on the type of vehicle. City officials said they couldn't verify that purchase, saying the trays are usually bought in bulk with the battery. Other city purchasing policies, if followed, would mean paying about $240 for...