Final answer:
An economist would use the term external benefits or positive externalities to describe what happens when a shopper gets a "good deal" on a product.
Step-by-step explanation:
An economist would use the term external benefits or positive externalities to describe what happens when a shopper gets a "good deal" on a product. External benefits refer to the beneficial spillovers to a third party or parties who did not purchase the good or service that provided the externalities.