I solve this problem two ways: firstly by being very expensive, charging several hundreds of dollars an hour; secondly by only working on a time and materials b

I solve this problem two ways: firstly by being very expensive, charging several hundreds of dollars an hour; secondly by only working on a time and materials basis. This won't work for everyone. Fixed priced projects only work in a few cases where you know exactly what you are building. They are a lose-lose situation otherwise, with the client usually being the loser.