Earlier quoted context omitted.
Do you mean everyone in the same role, or everyone in the company? I guess you could argue that everyone contributes equally in their own way, but it sounds like it would be hard to deal with market rates. For example, if the market rate for a support agent is $30k and the market rate for a developer is $70k what do you do?
Pay market rate and be honest about it? I don't understand the problem here. Support agents are unlikely to demand a developer's salary.
This is, in part, because every job will value someone slightly differently depending on the unique situation.