How much does it cost to feed a beef cow to maturity?

A cow is already at maturity because cows, whether they're beef or dairy, are female bovines that have had at least two calves and are at least 4 years of age, which is the age of maturity for a cow. So the question is pretty much pointless. But if you were to ask about a beef heifer or steer or calf that is such-and-such months of age, that's a different story.