Mathematically profit is impossible
Suppose you live on an island with another person. There are 2 people on this island, you and your neighbor. You sell and buy to your neighbor.
Let's suppose you and your neighbor each have 50 coins of gold. The total amount of money on the island is 100 coins of gold. This amount is fixed and limited and we suppose nobody is counterfeiting money.
Let's suppose you decide to make a profit and start selling more than you buy. What happens then? It means that your neighbor starts losing money.
If you have now 60 coins of gold it means your neighbor now has 40 coins of gold.
If you have now 70 coins of gold it means your neighbor now has 30 coins of gold.
It is impossible for everyone to get richer at the same time. If you get richer, it means your neighbor is getting poorer.
How do you make a profit? By selling more than you buy.
According to Accounting, profit is defined as the difference between revenue and expenses.
Revenue is money that comes in.
Expense is money that goes out.
If more money comes in, you have a profit.
If more money goes out, you have a loss.
When you sell, money comes in.
When you buy, money goes out.
If you sell more than you buy, you have a profit.
If you are having a profit, it means your money is increasing. If you start with 50 coins of gold, with profit, your money may increase to, say, 60 coins of gold.
But if you have 60 coins of gold, it means your neighbor has now 40 coins of gold.
If you are getting richer, it means your neighbor is getting poorer.
Eventually the economic system will collapse. Your neighbor will end up with no money and he will stop buying from you, because he has no money!
But since you have money you may decide to continue buying from your neighbor without selling anything. In that case your neighbor will refuse to sell to you, because this money would be useless to him. What is the point of having money if you cannot buy anything?
Money exists only to facilitate the exchange of goods and services. If you have no goods and services to offer to your neighbor, your neighbor cannot give you any goods and services in exchange.
It is a win-lose situation, also called zero-sum game. It is not possible for everybody to win at the same time, for someone to win, someone else needs to lose.
It doesn't matter how many people are on this island, you could have billions of people, mathematically the situation is exactly the same. For a group of people to make money by selling more than buying, another group of people necessarily needs to lose money.
Of course I am supposing the total amount of money is fixed and limited and nobody is counterfeiting money and increasing the money supply.
This conclusion is very disturbing because economically I have come to assume that commercial transactions ideally are a win-win situation.
In the real world you may have win-lose transactions, but economically all transactions should be win-win situations.
The point is: how can you have a win-win situation? Mathematically it is impossible.