I've been noodling around Amazon for many years now, but never understood the "Subscribe and Save" option. Subscribe and Save gives you a 15% discount on selected items (food and other stuff) if you sign up for regular delivery.
It also gives you FREE SHIPPING. And I learned that you can cancel your order at any time, so you can take the discount and cancel. Many people do that. You can set your schedule at up to 6 months hence, so you have plenty of time to decide. (Note: I don't think intending to cancel is unethical. Amy D of The Tightwad Gazette said such offers catch many fish and you don't need to feel guilty if you are a smart fish.)
I finally figured this out when I got a crisis email from Miss Em who seriously underestimated the amount of oatmeal--actually oat groats--she would consume. Mom to the rescue!
Then she requested some fancy tea. We were happy to oblige.
We are happy to oblige because Miss Em is a busy, carless student, and has less time to take care of these things than we do. Plus, of course, if your mother is pathologically frugal, it is a good idea to let her do the shopping. And, as an added bonus, parents end up paying! What a great system.
If you want to see where Amy D. takes her stand on the ethics of canceling a subscription after getting a benefit, well, it's somewhere in here.