Is $10 for a half-gram/a nic of exotic a rip off?

I don't know how much a gram/half-gram is. I asked and the guy I'm buying from said it was about a nic. He said it was exotic, and it'd be $10 for a half gram. $20 for a gram. Am I being ripped off or is that right? I've never bought and I can't really tell whats exotic and what isn't but I don't think he's lying.