This is rather a big issue in many industries I think, especially anything that is creative or does not require formal education (although even some industries with qualifications). I once worked as a computer technician and asking for a rate that made sense for me to work in the industry was difficult. Even more difficult was spending two hours doing the work and then trying to get paid, because they could not see something they wondered if you really did anything. Disheartening to say the least.