If you search the plural "die Gewinne" in a dictionary, it says the same thing as if you search the singular "der Gewinn". Also you could just aswell say "Unsere Firma hat dieses Jahr hohe Gewinne erzielt" as could you "Unsere Firma erwirtschaftete (or simply "machte") dieses Jahr einen hohen Gewinn." The verbs you use will change, but the meaning of the two sentences is absolutely identical. So Gewinne is just as accurate as Gewinn. It would be of course different, if the englisch word were "price". Obviously, you could not use the plural "Gewinne" in German in that case.