"This week's advertised special? Yeah, we've got that in stock, but you know--well, I shouldn't even be telling you this, but it's really not a very good product. Now this model here is a lot more reliable. It's a quality piece of equipment. It's more expensive, but you get what you pay for, right?"

Seriously unethical. Seriously illegal. If a business tries this on you, threaten to call the cops. You might get free stuff. Then call the cops anyway.