Probably true, but those are accounted for differently, and (I'd speculate) that public transit labor costs convert tax dollars into economic activity as efficiently as the route can possibly operate given the constraints on the rest of the system. The lower the overhead to buying busses and the more reliably you can run them, along with making them more usable by your regional population, the more efficiently you're moving people to their jobs and the more of the tax dollars allocated to transit can into the pool that's going into the economy.

All the busses and tools required for maintenance are capital assets amortized and expensed over years, while the roads and the other infrastructure are hugely expensive and are rarely used as efficiently as they can be.