Get a grip and relax...
Free as in, I already pay for prime so I'm getting something in addition to what I was expecting for nothing more. Sounds free to me. For some it may not be.
At the end of the day it's your money if you don't want to spend it don't spend it, nobody is forcing you to buy amazon e-readers, there are others on the market,. Nobody is forcing you to buy amazon's eBooks.