For this particular client, it is probably too late. No wonder they were happy with the price, they are getting you as an outsourcing firm to accept all of the risk and overhead of the work for less than they probably spend to have an employee to do the same work per hour. Companies pay a big premium to outsourcing firms because the firm takes on huge risk and is only paid while working whereas an employee has to be paid when there is work or not. But in this case, you are so cheap that they can't possibly turn you down.
Assume that this client is a lost cause, they will never be okay paying real rates, the rates needed to keep eating while doing this kind of work, after getting you for this price. Nearly everyone does this with the first client or two. Sadly, it's a burned bridge, but it is good learning. Most of any IT consulting is the business side. There are plenty of good IT people out there to do the technical work. It's the business setup, marketing, sales, billing, accounting, etc. that is hard to get and what makes all of the difference.