And the "reasonable" is in regard to the legal reasonable person, not to the individual in question, so "I just thought it sounded like a really good deal" isn'

And the "reasonable" is in regard to the legal reasonable person, not to the individual in question, so "I just thought it sounded like a really good deal" isn't really a defence (that's how we spell it here) unless you had equally reasonable grounds to believe that the deal was square. If there's one really cheap bike at what appears to be a yard sale, you're probably okay, but if there are ten of them, well, you're legally expected to be at least a little suspicious.