https://rady.ucsd.edu/faculty/directory/gneezy/pub/docs/fine...
Here's a digestible Freakonomics bit which discusses the same:
http://freakonomics.com/2013/10/23/what-makes-people-do-what...
When there was not a price on being late, the price paid was actually moral. That is, being late was a bad thing to do and so you should feel bad. However, when a monetary price was introduced, it was no longer morally bad to be late, as long as you paid the fee. The monetary-price replaced the moral-price, and it ended up that there were a lot of people willing to pay money where they weren't willing to pay morally. And so the truancy rate rose with introduction of late fees.
I would guess that that is what OP meant. If you introduce a price, you can actually remove even stronger restrictions that are in place based on morality. Because as long as you're being charged, you can assume the price is inclusive of your moral hazard.