When you buy a sheep, how much is it worth to you, what is its value? For starters, its value is at least what you paid for it, but that’s not quite it. Say you paid a hundred dollars for it. If you want to sell it now, how do you determine your selling price? A hundred-twenty? A hundred-fifty? Obviously, you need to increase the price by some percentage over whatever you paid initially, but regardless of what you increase your price, if you don’t know your true costs, you might be at loss.