I used to work in e-commerce, and one term you might not heard of is called an "abandoned cart." It is when a user is about to check out, but then leaves the site. This happens frequently, and many savvy e-commerce sites try to recover these abandoned carts.

If you got through much of the process including entering your email address, and abandon, the e-commerce site might send you an email within 24 hours to recover your cart and get some discount on checkout. This happens a lot on fashion and luxury purchase websites which have big markups from their production costs, and thus they can shave off a sizable percentage and still make a profit. 

So if you are on such a website, go through to the last page of checkout, and leave. Check your email (and your spam folder the next day) and you might have a surprise waiting for you.