I can envision scenarios where you're buying multiple copies of these things - gifts, book clubs, etc. Advertising doesn't have to work universally - it just h

I can envision scenarios where you're buying multiple copies of these things - gifts, book clubs, etc. Advertising doesn't have to work universally - it just has to work better than not advertising at all. I could very well imagine situations where it is cheap enough to advertise to everyone who has purchased those same items to get additional sales from those duplicate purchases and make money after the advertising spend.