Infrastructure for cars is massively subsidised too. Since tansport is infrastructure it it interacts with everything else (eg less cars in the city => less spending on car infra) and has a lot of positive externalities. The investment pays back in positive outcomes which can also be quantified in terms of money of you like. It's like you've got a balance sheet but you're filtering it to only look at two items.

Additionally, the other poster failed to mention that the unit economics for the marginal rider are much more favorable.