I recently stopped at $3 Car Wash - that's the name of the business. I pulled in, got in line and just waited for the "bait & screw", as in ... It's $3 after midnight or some such off-putting restriction.
When I pulled in, I saw the sign, "free vacuums" and then I proceeded to a touch screen that had four options for car wash ... $3, $6, $9, $12 - all the amounts included the tax, so the cost was exactly the stated price. I selected $3, glided through the many rows of bristles and suds and was on my way. I was thrilled.
On the other hand, when I buy a $5 Foot Long at Subway I always feel snookered, even though Subway is not doing a bait & screw, per se. Subway is very clear - the sandwich is $5 (plus tax), not the full lunch. Subway tries to up-sell the full meal or to add a drink and/or chips to the sandwich purchase. So, my lunch always costs more like $7 or $8.
Make a compelling promise and then deliver - what a concept. It's not about legalities, it's about a relationship.
O.D.O.o.O.D.B.