A product on Amazon has a market price - the thing being exchanged is an objective, metaphysical fact and people assign it a value. In areas of labor where the uniqueness of individuals is less of a factor, you will generally find that pay transparency is the norm. This is often unskilled/low-skilled labor in jobs that cannot offer meaningful non-pecuniary compensation.
But most people do not work in such jobs, and even in most manual labor jobs there is a strong element of applying your mind to do good work. As such, your purpose as an individual is much more important.
Pay transparency detrimental to you, as an individual. To live a happy life, you must figure out your own purpose and use your mind to achieve it. Happiness is not the result of income, nor is money required to be happy. Your happiness is a function of the achievement of the values you have defined for yourself. If you allow the income of others to influence your decision making, you are only hurting yourself. You should not leave a job that is satisfying in its essentials - that is, it fits with your purpose, you do meaningful work - merely because you discover someone else makes more; that would only hurt you. You don't know - can't know - their purpose, their value, their preferences, that lead to their income and work environment.