Stores underpricing one another is not the same as a manufacturer selling the identical item for dramatically different prices at different shops. This is because retail stores are allowed to control their own profit margins and if they wish to take a loss on an item, that is their prerogative. If all shops (or a group of shops) chose en masse to price consumers in certain geographical locations or buying groups out of the market while offering affordable prices to other groups, that is called collusion and it is illegal.
When a manufacturer itself chooses to make a gross profit at the expense of some customers to subsidize smaller profits on the backs of other customers during the same time frame (i.e., boutiques charge $100 and outlets charge $50 for the same item at the same time) without being overtly transparent about the practice it is tantamount to collusive behavior and is definitely on the margins of ethical practice. That is why the two items called out by OP have different model numbers... it is a deceptive practice designed to exploit anti-trust laws.
It is NOT the same as "Friday we charge one price, but on Saturday we have a sale."
I get what you're saying but I don't know any Coach customers who aren't aware of their pricing structure (though I'm sure there are a few). If their pricing structure were in fact illegal I'm sure action would have been taken long ago. To me it's more of an "annoyance" issue when customers find out they could have had the same item for a lesser price.