Say you want something. You want something real bad. You are willing to sell your soul to get it. Okay, you go for it. Soul sold. Now what? Inevitably you are going to want something again just as bad. But now you don't have a soul. You don't have anything to bargain with. The Devil is just going to ignore you. But what if you could buy a soul yourself? Replace the one you already bargained away. At Secondhand Souls we have a soul for you. Now the Devil's going to take notice. We put the Devil on your other shoulder!
The problem is the cloned souls aren't that valuable to the Devil, let's face it. He knows it's a copy. Don't expect him to provide you with your biggest desire. The best you could hope for is maybe something small, maybe something like a sandwich if you're hungry. Of course, knowing the Devil, it would probably be a sandwich with thorns in it.