If I know some information you do not and I make a trade with you based on that information to my gain, that is not fraud. There are rules that could put me in the "insider trading" target, but there are plenty of situations that don't. I might have done better market research than you did and know that some commodity is about to jump in value or some company is about to become more valuable due to some other activity in the world. Me trading on that information is not fraud, it's smart investing.
You examples are fraud and maybe (?) fraud. I'm not a lawyer so I couldn't say if lying to someone selling you something about it's value is fraud or not. Morally it's wrong, sure. Legally, I have no idea. Both of your examples are, IMO, bad.