Paula Scher, in her book Make it Bigger, discusses the negotiation process that goes on between the designer and the client.
A correlative to this rule is that apparently simple jobs are rarely that. When a client once tried to persuade me to cut my fee on a “simple” job, I told him that I needed the money to pay for all the changes he was going to make. He insisted that the project was uncomplicated and that there would be few revisions. I offered him a deal: the design would be free, but every revision made—no matter how minor—would cost a thousand dollars. He refused the deal.
When my design failed to make it through the bureaucratic gauntlet, I found that the project would be reassigned to a large, powerful design firm for a large, powerful fee. I discovered that clients tended to respect an opinion in direct proportion to what they paid for it. The quality of the design was often irrelevant.