Don't confuse this with 'accounting profit', which is what most people generally mean when they refer to profit.
In calculating economic profit, opportunity costs are deducted from revenues earned. Opportunity costs are the alternative returns foregone by using the chosen inputs. As a result, you can have a significant accounting profit with little to no economic profit.
For example, say you invest $100,000 to start a business, and in that year you earn $120,000 in profits. Your accounting profit would be $20,000. However, say that same year you could have earned an income of $45,000 had you been employed. Therefore, you have an economic loss of $25,000 (120,000 - 100,000 - 45,000).