>"Now that they've captured 50%+ of US ecommerce, they've also raised many prices, to the point where they're far from the cheapest price in many cases."

This has been my observation as well, at least for a basket of household sundries and office supplies I was previously sourcing from Amazon. They were often more than a few dollars cheaper at a local store. I realized I had fallen into the too complacent to price shop trap for a while. I agree with your other points and for me deliveries issue started to become a regular occurrence. I think the bloom is off the rose with Amazon.