The best way to ruin the day of a Moroccan is to accept the first price they offer to you for something that you’re going to buy.
This is so, because they will then spend the whole day wondering how much more they could have gotten from you since you accepted his first price.
Bargaining is a fundamental part of the Moroccan life and is part of the culture. It is employed throughout all of the Moroccan markets, and it is recommended that you bargain to agree on a price when taking a taxi.
However you should do this before you get in a grand taxi, rather than when you get to your destination.