>On the other hand, Amazon delays orders on purposes if you aren't a Prime member.
I'm not so sure about this. I'm not a prime member and I frequently get orders delivered before the estimated delivery date. On the other hand I also see instances where amazon takes suspiciously long to ship something. A charitable explanation might be that their logistics capacity (eg. planes or vans) is limited, so if you're not a prime member you get deprioritized.