Don't believe there's a maximum - fees must be reasonable considering the scope of the representation, skill, training and eduction of the attorney and the nature of the matter. It's like asking what the maximum price of a house in MD can be - depends on the house and the market.
Good luck.
Non attorney petition preparers fees are regulated by the office of the United States Trustee. I have never heard anyone claim that there is a secret as to the amount. Each local office can establish the amount a petition preparer can charge.
As to attorney fees, in Chapter 7 the amount is limited to a dollar amount. Hope this perspective helps!