Here is why i originally bought Amazon Prime: because it was taking a week to get an order. Not because shipping took a week, but because packing often took a few days. Prime forces Amazon to prioritize my orders. That means costs beyond what they would be paying if they could ship 5-8 days. I can imagine these costs to be increasing over time, not paying the shipper mind you, but paying enough staff to pack so that my order leaves the warehouse in time for the shipper to get it to me in two days. All for $100.
If I order a $20 widget a week, that is around $2 per package shipping, around $1000 revenue, and probably zero profit. Yes, amazon is shaking in it's boots because people who only use shipping are going to cancel.
OTOH, if I didn't have amazon prime I would be more likely to shop elsewhere.
In any case, remember that Samsung, which is what most people buy when they buy an android phone, pays MS $10-20 per phone. This is clearly where MS future lies, collecting patent fees. The only reason that it needs to have a phone is so it is not labeled as patent troll.
Less efficient not only in fuel consumption, but also in road consumption. A while back Texas A&M did a road study on how traffic is effected by these large trucks. One finding is a stop lights they take about 1.5 times a long to transverse as a car. Check which cars make you miss the light next time you are trying to go through an intersection.