Do you present project proposals as lots of little releases rather than one big price?
When a prospective client gets a quote for a huge price it's like giving them a slap in the face. Break your proposals into a series of releases, where each is 1 or more sprints, and clients can choose to proceed with a smaller financial commitment (such as just getting the mock-ups done) than if they were committing to the whole project. Often, small financial commitments will lead to bigger ones.
This approach also allows you to side-step common delaying tactics of prospective clients by making it easier to get the project moving.