I refuse to talk cost until they have a way to judge value. For example, i might turn a spreadsheet into a program. It won't have everything but they'll be able to see something. Then I can say, OK, this is what I did, this is working, this isn't, and it took me X hours. Now I can tell them my rate and they can judge value. I've never failed to get a client once I was able to get them to that point.

Usually explaining that paying me £x per day works out the same or just a little more than the equivalent salary for a full time developer, works ok. If they still complain after that then I usually don't take them on unless I'm desperate and give them a rates cut.