HP has teamed up with Starbucks to offer great deals exclusively to Starbucks customers. This reminds me of a technology body shop I consulted through once - ONCE! – that offered "great deals" at PC Connection. I checked out some of these deals and found discounts as
low as five cents.
The systems of motivation in these two cases are different, but there is a similarity: there's little to nothing in it for the deals' recipients.
Postscript: I would verify that this is actually true in the case of the HP offer, but you need to sign up for an account before the site they link to will give you any prices.
What's in it for Starbucks? Money, I suppose. They're not just selling coffee and muffins to their customers, they're now selling their customers' attention to HP. And they may think that their customers will thank them for being so nice as to "partner" with HP to make these kind offers.
What's in it for HP? Association with the Starbucks lifestyle brand. HP is apparently going for the Tim Burton-loving, Jonathan Safran Foer-reading, caffeine-addled pseudo-bohemian segment. They get the perception of doing a good deed and offering good prices without the need to give a significant discount. And this works for people taken in by the promo piece, regardless of whether or not the make a purchase.