A system like this encourages others to compare salaries and make judgements about oneself related to how well one is doing compared to someone else. This creates unhappyness because some feel they work harder and shouldn't be paid a quarter less. The person getting the extra amount feels they are more successful than there peers. All this does is distract you from the fact that both of you are making only a few dollars above minimum wage. If you only look at total pay in relation to your needs you will accept and be proud of your wage.
I have seen people who love there job find out someone they feel does not measure up to them make more money. This causes them to start hating the role they once loved and in some cases they left for the same salary elsewhere.