A lot of restaurant soups come from packages. The Campbells Soups come in an institutional size and follow a different recipe than the condensed stuff you buy in the store. Harry's Fine Foods, a company in Portland, OR, produces a large number of packaged soups for restaurants in small batches as well as making grocery store label soups, like Safeway's fancy soups.
Some, however, do not--I worked at a restaurant over the summer and we made our soup from scratch every day.
Soup is actually one of the easiest things you can make, so do try.