Businesses love subscriptions too. Get paid even when they subscriber doesn't do anything? Yes, please! So now we've combined lock in and subscription.
We hear Zynga makes a ton of their profits from whales, so low numbers of prime subscriptions doesn't really scare me. Those are whales.
Amazon is a business, if they haven't already figured out this will make money and it doesn't end up making money, they'll stop after a while.
Makes plenty of sense to me. This isn't a big deal.