Do you do job-based consultation? Say one has a project/website, and that person has some marketing goals in mind, can you quote a price instead? Also, any guarantee on effectiveness?
Projects I take on aside from this I usually tie goals and performance metrics to. It very much depends on the goals and objectives to be achieved for the project.
For example if your project is to take an iOS app from 100 users to 1,000,000. That I wouldn't take on as a project, that's what someone should take on as a career/job more than a contract. 100 users to 10,000 is something I would consider freelance/contract size.
Marketers on Demand was setup as a test of the 7 Day Startup framework and to run an idea validation thought. Not really for full on projects.