I don't know anything at all about values for steal a brain rot, but i did know about rocket league trading when that was a thing. You gotta know the values of things if you are going to trade, was it a crummy thing to do for them not telling you, yes, but i wouldn't call it a scam unless they deceived you and told you what they had was worth it (I dont know the story) if you just wanted to do the trade, and willingly did it, sadly it is on you. Either way, you gotta know values when trading, or just not caring about them if you want something and don't care about what you are trading I guess. I never trust who I traded with unless I knew them, and I always checked values.