Amazon is a separate revenue generator, not combined with HP Ads.
I usually include a couple of Amazon capsules in my hubs-- sometimes they just act as a nice graphic to enhance layout, or to show a book or two related to my hub subject.
I don't earn a lot from them-- maybe 10-15$ per month, which is credited to my Amazon account. I buy from them often, so it's always nice to have a little discount.
Also, since I have a book on Amazon-- I'm likely to show that if it is relavant.