In the long term of human past history, the salary, the pay, the reward is basically based upon individual contributions whereas the root of the problem consists in a fallacy that not any system can literally measure how much an individual is really contributing to a society and more often than not, the contribution is often heavily dependent on the contexts, where, how, what, who and when.

Supposing you are walking in a dire hot desert, it goes without saying at that moment , water is the most useful resource to be featured rather than valuable jewelries or diamond. In that case, the people who can hold the water resource can gain the profit from the scarce resource.  Nonetheless In an extremely developed capital society, we can think jewelry deals might be easy to be rewarded a lot who  might be totally useless in a desolate horrible jungle.   

Some people say it would be better for society if everyone got the same salary. What do you think about that? Why?

That is pretty fascinating a platoes' world that nowadays no society can really reach for the ideal world. Think about this: supposing everyone can do their best and get paid in accordance with their contribution, how to measure the amount of individual contributions to the society? Let alone as you said everyone is paid equally in the amount of salary without considering their individual contributions. 

However as a economist, we can change our mind to build a society similar, simulating the ideal society. The method is to practice the ideal distribution through relatively fair taxation on those people who earn more in a society to help some others living in the minimal  living standard with redistribution of wealth and boost those people living in the margin to brace up again, which is at present carrying on in a couple of countries with sound societal welfare. 

Anshu,

why cricket players are rich people in your country ? Cricket game is a kind of business ? It sounds unusual.

It depends on the education (mostly at least).

After 13 years of school and after you took your A-levels the starting salary is about 1500-2000€. People who have a craftman's trade start with a higher salary but I think they have less career opportunities. If you have a university degree you get a higher starting salary.

Some of the best paid jobs:
The average income of a doctor is about 90,000€ in one year, there are also some who earn 300,000€.
There are also jobs in the financial sector which promise 40,000€ up to 300,000€ as well.
Also politicians earn a lot of (unjustified in my opinion) money. The chancellor's salary is about 280,000€, the president's over 300,000.