Originally Posted by
flymonthly
While you responded to the situation described, that's not the question the OP actually asked - if airlines had to honor a ticketed price. The correct answer is that there is no law, but there is a DOT rule that airlines have to honor a ticketed or purchased price (or risk being fined by DOT).
The DOT rule says they can't charge mandatory additions to the fare once ticketed. Whether that means an airline can cancel and refund a mistake fare is somewhat open for debate.