@gogola I believe is a multi way deal between people trying to get something for their existing Amazon gift cards and willing to take a hit on their value for a quick bitcoin buy, and thrifty buyers. Sometimes instead of gift cards it's third world countries folks trying to get a payment for mechanical turk work.
If my explanation is clear as mud, it may be because I tried to string together what I think I am understanding from googling it...
Key features include an instant 5% savings on any items bought from Amazon using bitcoin, viewing and tracking pending orders, and integrated Purse support. Using the app, users can also save more by creating Amazon wish-lists, pasting them into the search bar to add them to their cart, and choosing how much they wish to save with Name Your Discount to save up to over 30%
Crumbs App
CNVS
Purse iOS App