Well, duh!
2) You may order enough items to get to the point where your avoided shipping costs exceed $79, but if you think you didn't pay for it you are fooling yourself, and trying to offer up your self deception as a rational argument.
I used it once. Then I canceled within the free trial period they were offering. But that doesn't mean it's not a clever idea.
3) Amazon is not going to pay any more or less for the cost of shipping because you have given them $79.
Duh, again.
4) Amazon is not a shipping service. You are citing them as as if they are the equivalent of UPS, or FedEX, or USPS; they're not.
No, they're a Luddite-annoying service.
And, BTW, although they sell plenty of physical goods, they're also making a lot of progress moving books out of the shipping world and into the world of pure information.
To quote your inane response: well, duh.
I'm glad you have, once again, agreed with me. The next time you initiate a debate try to grasp all of those "duh" concepts before you manage to forge ahead full circle to the point where you concede. It will save everyone time.
I'm not sure if you are failing to grasp what others are writing or what you have written, but you really need some help in that area. I am sure that I would rather not provide lessons. Good luck.