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.

Maybe in some way worker strikes also have an influence on people's buying decisions.

A lot of my friends  and I have decided to reduce the amount of things purchased on Amazon to the minimum due to Amazon's poor treatment towards their entry level workers.

I personally use Amazon to search for stuff that I later on try to find on local stores or, if I can't find it in a local store, I try to buy it from another online retailer.
Only if price differences are really really big or I can't find it elsewhere is when I actually buy it on Amazon, which in the last 6 months has been reduced to only a couple very low priced articles.

Adding up to that, Prime prices have gone up where I live with no actual benefit, so I'll also definitely cancel my Prime subscription when this year's subscription ends.