Here is your inconsistent position

"Now, do you really want to take a $400.00 chip from him for $100+, because the poor guy was ignorant and misinformed? If he was your next door neighbor, or a friend or coworker, or your son, would you feel the same?"

Now how is that cocnsistent with your taking the ivory chips at $6/ea because of the mistake your seller made?

You suggest that Jim would be morally wrong to take advantage of the Seller's mistake (and you might be right) and Katie suggests that you might be wrong to take advantage of your Seller's mistake (and she might be right).