Clients think you charge too much?
A Wharton professor did a study of whether consumers thought prices were "fair". Most of the article talks about their studying process, but they concluded that -- when asked about "fairness" -- most college students concluded that other people's pricing decisions were not fair, and were "greedy".
This study seems to suffer at least two vulnerabilities... they used only college students as sample, and focused on "fair" rather than "desirable" pricing. (The term "fair pricing" carries a raft of implications, the biggest of which may be the assumption of objective and universal truth and which discards the possibility of differing relations between consenting adults... wacky religious stuff, that.) For sampling problems, that study may have benefitted from comparing results from college students who had not had a job from those who had, and from those who had entrepreneurial experience.
Anyway, if you're negotiating prices with your own clients, it may be better to stay away from conversations about "fair" and "unfair" and instead focus on what they want, and how much it would be worth to them. This study is interesting reading, but I'm not sure about its assumptions and conclusions.