An answer to a question on whether promo codes do more harm than good, mentioned that 27% of users will abandon a shopping cart to look for a promo code. As a follow-up, are there any statistics or studies that tell what percentage of those users looking for a promo code come back?
from personal experience that's really annoying to see there is a place for a coupon, because most of the time you don't have it which makes you think: ok, where the hell am I supposed to get a coupon from? and that you google and don't find anything and it all leads to more frustration
my point is coupons work only for coupon junkies who are constantly looking for the deals and wait for their moment to seize it
I think it depends on if your price is already competitive. They may find a competing ad and determine you're still the best price and come back to your site without a promo. On the other hand, the opposite can happen. Know your competitive landscape.