In this economy, lawyers should be entrepreneurs who have good insight into more subjects than just the law: marketing, social media, and how to run a small business. You may not realize it, but that is valuable knowledge that you need not provide for free. When someone wants to hire you as a consultant, make sure you know how to set your rate.
One theory is to ask what the client is willing to pay. There is some value to taking that into account, but hard to justify to the client when ask for an explanation of your rate.
A better way is to find out what others charge for similar services. That might be difficult to find out, but it is starting point. If you cannot find any similar providers, ask your colleagues what they would be willing to pay for such a service. Better yet, what would you be willing to pay for it? Most likely, you will undervalue yourself, and so will your friends. Be sure to remember that when deciding your rate.
Another option is more creative approaches, as outlined here. You might consider a contingent-fee or a flat-fee arrangement. Whatever you decide, make sure it is a rate and an agreement you feel comfortable with.