A long time ago I worked out that business is all about numbers, but not the numbers many people, including Bezos thinks are important.
First off, the price of the product is only important in relation to the manufacturer's overhead, and what it means to the bottom line.
Secondly, quantity is like market share and turnover - pure vanity, and in the case of all three, a hostage to fortune. Eventually, oversupply will kill the market, it's only a matter of time. Chasing any or all of them will eventually kill the business.
Finally, after all the overheads and the revenue has stolen its share of unearned luka, there's the gross profit - the only way you know a product is REALLY making money.
When Apple released the first iPod, it was $400 - way more than the competition. They didn't, as Amazon is doing here, sell it at a discount to entice customers into buying music from iTunes Store. Indeed, iTunes Store wasn't launched until 18 months later.
Now, that model works, we know that. Everything else is a 'me too' spoiler by lesser players.
Maybe families - when they are all together, as suggested in this ad, can share their devices, but is that really how we work? No, we have our own devices, we don't rely on others to provide the unit backup that's lacking in one device. So the ad fails the reality test.
And therefore the real final number that's important to business is one - the one product you get one customer to buy, that allows them to do everything they want to do, whether it's read a book, watch a movie, or shop - the unmentioned only reason Kindle Fires are sold so cheap - below cost. But that shopping should be possible anywhere, not just at Amazon.