So using the above logic should a merchant be required to tell every customer that if they had a coupon from the local paper they could save money?
No - the local business does not have a contract with their customers that says they will get a discount on their product... banks do. Banks have a contract that says "open this account and we will give you an extra .10% on all your CDs" - banks are obligated to make sure that happens.
Now I must admit, I think the "Guaranteed Lowest Price" that you see at grocery stores and home improvement stores should be a UDAAP violation... it isn't my job to make sure I am actually paying the lowest price if they are guaranteeing that it is. And don't get me started on car dealerships - I don't see how they get away with half of what they do. I mean...
only $599/month for an E-class Mercedes, just pay TT&L and a $5,000 down payment for 24 months and then another $40,000 at lease end to purchase the vehicle or $500 return fee. (font embelishment is intentional) If it is "only" $599/month, how can you be charged everything else?