By Chris Lisinski, State House News Service May 13, 2021 Chris Lisinski, State House News Service Offering all MBTA bus trips free of fares could carry a price tag of hundreds of millions of dollars, driven by both increased operating costs and foregone revenue, T officials said on Monday. As the transit agency weighs new low-income fare options and pushes toward an overhaul of how riders pay to take trips, MBTA staff outlined impacts that they believe could stem from eliminating fares on buses. Several elected officials, including Boston Mayor Kim Janey, have called for the T to make buses free to riders.