This is great! It's amazing how often the big question comes up, "How much?", before any of these questions are answered. I always start with a list of questions, but if they insist on a price I'll offer something so broad I could be developing a business card WordPress site or a full blown iPhone/Android app, "It'll be anywhere from $1,000 to $8,000, so let's answer some of these questions.."
Agreed, recently I got bit pretty hard on a project because the backend model was an API they were building out. However we didn't ask enough about the availability and data structure invovled, and so the initial deadline was far exceeded due to having to wait and debug the API that was assumed to be complete.