I also don't have Prime, and buy from eBay where possible, but a substantial fraction of the time, the things I buy turn up in Amazon boxes. I think there are e

I also don't have Prime, and buy from eBay where possible, but a substantial fraction of the time, the things I buy turn up in Amazon boxes. I think there are eBay sellers who have Prime, list items at slightly less than Amazon's price including shipping, then use their free shipping to drop-ship items to customers. They collect slightly less than Amazon's shipping fee in gross margin, and only have the Prime free as overhead.