Tickets may be cheap and somewhat eco-friendly if made from whatever recycled paper and a drilling machine like in the old days. But i doubt that's the case, so

Tickets may be cheap and somewhat eco-friendly if made from whatever recycled paper and a drilling machine like in the old days. But i doubt that's the case, so you have to account for the financial and ecological costs of all the electronics and magnetic tapes, and all the replacement parts you need to keep that system of control operating. Also, if your tickets are sufficiently unsophisticated to be eco-friendly, then they may well be very easy to forge. That is, without mentioning that controllers have to be paid without providing any service. If you additionally take into consideration the social cost of the criminalization of something as banal as using public transports when you don't have money, the benefits of doing away with these systems of control arguably are even more evident.