According to Billboard, participating labels entered into the program with Amazon in 2008 without paying a thing. It was simply meant to increase the store's publicity. Two years later, that's changed. An unnamed major-label head of sales told Billboard that "[the] promotion morphed into something where the labels make arrangements to provide an exclusive selling window with Amazon for a big release expected to do a lot of business on street date [the day the new release is available for general retail sales]."
Two years in, the labels are motivated to offer Amazon first dibs on major releases at a significant discount, and that's gotten Apple's attention. Billboard's sources suggest that iTunes executives are trying to persuade labels to stop offering Amazon these exclusives, and have even gone so far as to pull their own promotions for those releases.
In response, Billboard reports, certain label executives recently opted out of Daily Deal promotions for such big names as Corinne Bailey Rae, Lady Antebellum and Ke$ha (Sony Music Entertainment denies considering a Daily Deal promotion for Ke$ha's "Animal"). Additionally, Amazon is said to be altering the deal to not require exclusivity, but Apple's still unsatisfied.
Oh what a tangled web we weave, when first we practice to sell digital music.