BookRix is charging both an upfront fee (like BookBaby) and an ongoing commission (like Smashwords). The initial charge is $40, which is not so unreasonable - until you combine it with the commission. BookRix pays authors 55% of sales from their ebookstore, and 43% from 3rd party bookstores. By any standards, that is ridiculously low.
Perhaps I shouldn't use the word ridiculous, but let me give you yardstick. Smashwords pays a higher commission (both on ebooks they sell and vi 3rd party sellers), and they don't charge a fee. BookBaby charges a higher fee, but they pay 100% to the author. (They don't charge a commission, but there is a small yearly fee per title.)
Now, some might argue that BookRix offers a useful service, and that the ebookstore builds upon it. This is true. BookRix does let authors develop their work with community feedback, surrounded by over 400 thousand enthusiasts. And being able to sell your work to the community of readers around you is a good thing, yes.
But BookRix isn't the only book and writing community that does this. Have you looked at Wattpad?
They are even bigger than BookRix, and they have offered ebook distribution options since July 2010. That's when Wattpad formed a partnership with Smashwords. Rather than try to handle distribution themselves, Wattpad signed with what was the best self-pub platform at the time (still one of the better options). Wattpad also has Lulu as a partner, thus giving authors print options as well.
For the life of me, I don't see why anyone would sign up to distribute their ebooks via Bookrix. The terms of the deal are simply terrible; this is one case where virtually any other option is better.