Target's been fined tons for not honoring their mistakes. You could have gotten it for that price.
Price errors are common mistakes for retailers; unless it's intentional or purposefully deceptive -- all things big retailers like Target aren't -- there is really no reason for them to HAVE to honor it other than just wanting to be courteous to their customers.
Some folks here seem to think the law is a whole lot stronger than it really is. If they only knew that consumers have little to no power at all on 99% of the stuff that happens to them.