Upselling is the practice of encouraging guests to purchase higher-end food or drinks, for example, the server suggested an expensive dish.
Cross-selling offers guests a different but complementary item in addition to what they have already chosen, for example, the server recommends the wine with a pair of the guest's dishes.
Most restaurant managers or owners expect servers to sell expensive foods and wines.
Every guest has a different financial background and budget to spend money at the restaurant.
Upselling shouldn't have become harassing your guests to make them buy something they didn't like or need.
It always makes me feel uncomfortable because it does not make sense to me to try to sell something that people do not want to purchase.