Here is a side by side look at the checkout badges on AdWords. The $5 off version is the new version being tested, the other one is the normal checkout badge:
Google has a large FAQ on badges, but this $5 off badge is new. Steve asked Google about the new badges and received this response:
As part of this experiment, a percentage of search results on google.com will display the promotional badge. We’ve done experiments with our badges in the past and we’re committed to constant refinement and experimentation in the future. We have no further details to share at this time.
It seems to me that the “percentage of search results” that trigger this are based on the merchant and not on the searcher, but I can be wrong.