Stuff like that can and will happen to everyone, unless they take the time doing steps to prevent it. While I feel for you, I highly disagree with a lot of what you have said, especially things like "Most of your clients are shoppers...".

How can you put a numeric figure on what other people's clients are? Maybe yours are that way, but I know mine sure aren't. My clients know they're going to get something quality when they hire me and as such, they ignore people trying to lowball me to get work and stick with me even if it means more money out of their pocket.

Out of curiosity, did you and your client sign a contract?