***If I sell my services to one client for $X and another client for $Y, neither one of them has any right to know what the other one is paying.***
That is a very Biblical way of doing business. In today’s climate, I hope you can maintain the veil. If you truly have one. One caveat, the government has no such leeway in the open. What it does behind closed doors is another subject. Are you perhaps behind one of those closed doors? Forget I even asked, of course you are not.
Some of my clients are subject to public disclosure rules -- mainly, they can be audited by government authorities at any time. My company would be completely off the radar screen because I am way too small for a government auditor to care about, but in these cases I try to be consistent in my dealings with the clients. I would probably be consistent anyway WITHOUT the audit issue, since the work I do for these clients is generally similar and would generally similar and subject to the same competitive pressure in my industry.