Thank you for writing this article. Like you, I found the first book in this series unreadable. Naturally, there was no point attempting the others--and certainly no point watching the films.
It wasn't until I read your article, however, that I understood something about this series neither the author nor the producers seemed to have in mind.
The relationship in this story is a metaphor. Christian Grey is a stand-in for money as the power principle. Anastassia represents those without money who find themselves in its grip, manipulated, abused, and tricked into making deals that will never work for them.
As you rightly point out, she has made a Faustian bargain in exchange for a gilded cage that will never replace the dignity and self-respect she loses in the exhange.
The success of this story exemplies how these values are sold to the powerless masses. Not just sexually but collectively in the body-politic.
Although there "may" be an argument in favor of a certain kind of BDSM relationship from a psycho-sexual perspective, this story does not appear to understand the potential psychological advantage of that argument. Nor is it interested in promoting anything but its own financial return. In other words it would seem that the author, publisher, and film producers are essentially Christian Grey--and the rest of us, unwitting Anastassias.
I'm very glad you wrote this piece, and I hope you won't mind if I share it onTwitter, Facebook, and refer to it here on Medium. If you'd rather not, just let me know. It won't change my gratitude to you for expressing your views with clarity and courage. Best wishes to you!