Good insight, heffeque. I think the rise in Prime subscription price is definitely slowing the Prime business. Anecdotally, I know of several people that did not renew their Prime subscription because of that. Buying a Prime subscription in October would also make sense as people gear up for the holiday season and Christmas shopping, so it could be that a number of Prime subs fell off this month. That's just speculation at this point, though.
Either way, America's retail consumerism is starting to stagnate; I think people are starting to feel pressured into buying the shiniest thing every year, and as technology improves, prices come down. Look at the smartphone market; people are holding onto their smartphones for a lot longer than they used to. The single-year upgrade has been drastically cut, and the two-year upgrade pattern is also slowing.