It's not the place of any person on this planet to tell someone that their belief system is false. Mainly because you don't know that.
I'm all for being realistic, Asrik, but it's uncalled for. You keep your beliefs to yourself, if you'd please, because I highly doubt you have any lick of evidence saying that "Satan" in any form, does not exist.
Dreaming about Satan offering you something for a trade does not necessarily mean it has to be a certain belief in, or fixation with Satan himself.
"Satan" in the context you described him Twix, is not only a person/entity of extreme greed, but he's an icon of fear, and "sin". Perhaps you have a longing for something, and your depiction of Satan appeared in your dream because it best exemplified your strong desire, while on the other demonstrating a possible timid, or cautious stance on the situation.
Then again I could very well be wrong, and you could just be dreaming about a scary demon guy wanting your soul.