They calculate costs and anticipate contingencies.
Unanticipated costs are the bane of good business.
This applies to all sectors of commerce. Imagine that you import a container-load of a processed food product from a country in the Far East. Imagine further that you are aware that the product is subject to a U.S. antidumping duty order, and that you must make a 10 percent ad valorem deposit to the U.S. Customs Service upon entry of the product. Obviously this additional cost is an unpleasant burden. However, because you are a knowledgeable and astute importer, you account for the burden in your price.