> If you're holding a yard sale, and I point at some knickknack and ask "how much for that?", and you say "it's a dollar" and I say "that's a deal", that's a contract.

If you move forward and actually execute on it, sure.

If you then immediately say "actually, no, I've changed my mind", without making any motions to give the item over, it's hard to imagine that'd be considered breach of contract.