The trolley analogy doesn't really hold up in this context, does it?

The incentive to do the right thing that a coin-deposit shopping cart ("trolley") adds is the ultimate return of that coin. It's not much money, but it is nonetheless returned when the cart is put back where it belongs.

If a cart always costs 50 cents and there is no hope of ever getting that money back, then: The monetary incentive to return the cart doesn't exist.

Well, even if you don’t get your 50 cents back you usually have an incentive to leave the restroom when you’re done.

> If a cart always costs 50 cents and there is no hope of ever getting that money back, then: The monetary incentive to return the cart doesn't exist

The grandparent post is just talking about incentives.

I guess what you're saying is that if you pay 50 cents for the bathroom then there's no actual incentive to keep it clean because the 50 cents is gone either way, unlike a cart deposit?

You're probably right about that, but I also don't think most people actually need an incentive not to make a huge mess. I would put money that most messes in public bathrooms are caused by the people that the 50 cent charge filters out. The rest experience some social pressure from the attendant to keep things clean. If all else fails, the attendant can clean up a mess before the next person uses it