The question is "what reliable external source do we have for other styles of campaigns?" If they'd stuck a (unique) phone number there - how many calls would it generate? If they'd used a (unique) SMS promo there - how many texts would it generate? If they'd printed a (unique) URL there - how many hits would it have got? The answer is....? I don't know. I'm not aware of anyone publishing independently verifiable response rates for those sorts of adverts. If you know someone who is, please tell us! 17K could be fantastic, it could be 1% of what an SMS promo would bring. What I do know is that 17,000 scans feels like the start of something big.