However, one needs to really figure out whether this habit actually helps shoppers save money, or make them spend even more than they would normally do.
The grammar in this sentence is a little messed up.
The question is not very good, because obviously a sale benefits shoppers if the sale price is lower than it normally would be. The extent to which it can make them spend more than they normally would all depends on how well the shoppers can resist the urge to overspend and how well the sale presentations encourage them to overspend.
I think it is not fair that they make you take a stand for one side of the question or the other. Sometimes things are not so simple! :-)