Even if it were free, it would be useless. A machine simply can't read it for you as a reader would. Ever. As far as cost, editors and beta readers somwtimes offer deals, you can go in as a group, some groups offer for free sometimes, probono groups exist, trade in-kind skills exists...

and like it's not free no matter what they say! you are paying it every single word you wrote and put in the thing! like come on!