It's not fair to compare advertising bucks on an apples to apples basis. Amazon has something on their store below every book which is available for the Kindle

It's not fair to compare advertising bucks on an apples to apples basis. Amazon has something on their store below every book which is available for the Kindle (which is most of them by sales volume) saying "Available on Kindle". The cash value of those ads would be enormous, far, far more than Sony has spent I'm sure.