It is against their Terms of Service to try and profit by click differentials (ie - paying 5 cents a click in adwords to try and earn 10 cents a click from adsense)
I think you should adward for product and service and not for adsense only. Take adsense for some extra bucks. If you have or planning a site for adsense only then you should convert it into affiliate. This way you'll get two way income. You can also use adward then. I think so.
It will be better if you advertise in adwords for affiliate products, then you can earn good profit. By using adword adsense combination chance of getting profilt is very less.
I do not very much about amazon store, but I think amazon store is in amazon's domain. You better ask them whehter they allow adsense on it or not. If they allow then it can become profitable to bring visiors to amazon's store.
I tried advertising a site with adsense through adwords briefly, albeit for a small niche site. It was a money loser; the traffic from the adwords clicks resulted in no measurable increase in adsense income.
You can create your own amazon store in your own site like mine http://store.best-cellphones.org/ what I am not sure is that if google adsense will allow me to put adsense in this type of site. So that I can use to promote in adwords