Suppose you were working for a wealthy company and you see management pay an employee with the initials A.M., who takes a TON of sick days every year, and who you out performed the last 2 years, $116,000.
Then suppose you see that same company pay a useless employee (with the initials W.N.) $66,000.
The company then comes to you and says, "We'd like to pay you the same as A.M., since you produce the same and you never take a sick day, but we don't have the money in the budget. We hope you understand."
Would you understand or would you say "Screw you! I want the same as A.M. and way more than W.N.!!!" Most people would choose the latter. I know I would.