Several EU cities have experimented with making public transport free, and people seem to really enjoy it.
Also, as you so eloquently put it, it isn't clear that the cost for issuing and checking tickets is covered by the income from the tickets, and there are reasons why MTA tickets cannot be priced at the actual cost to cover the ticket compliance infrastructure -- with a nice analogy to the cost of parking vs value of parking real estate. What justifies the subsidy for on-street parking?
Some internet searching suggests fares account for between 25 and 33 percent of the MTA’s revenue. There’s no way the infrastructure for collecting fares costs that much.
This is one of the main criticisms of free fares: in reality the revenue stream from fares is never actually fully replaced, so it just results in the transit agency becoming underfunded. This makes transit worse for existing users who are already paying. The new users you get because of free fares are mostly casual users like tourists who have alternate options, so serving them isn’t that useful and not worth the negative impact on existing users.
Also, as you so eloquently put it, it isn't clear that the cost for issuing and checking tickets is covered by the income from the tickets, and there are reasons why MTA tickets cannot be priced at the actual cost to cover the ticket compliance infrastructure -- with a nice analogy to the cost of parking vs value of parking real estate. What justifies the subsidy for on-street parking?