In Capitalism, there is the so called "supply and demand" theory.
It is a theory that price of a product is determined by its supply and the demand for it on the free market.
Here are the three problems of the free market.
Problem 1 - Demand greater than supply
If demand is greater than supply, every economist will tell you that prices must go up.
Problem 2 - Demand equal to supply
If demand is equal to supply, prices again go up because anyone selling products at lower prices will quickly run out of them, and those who sell at higher prices will become the only sellers and will earn more money.
Problem 3 - Demand lower than supply
Many economists falsely believe that if demand is lower than supply, that prices go down.
That is far from reality.
When supply exceeds demand, what happens is not that prices go down, but capitalists reduce production to reduce supply.
After supply is reduced and becomes equal to demand, we again have Problem 2.
Also, there is the cost of production effect where even if supply is higher, price cannot go down as cost of making a product wont allow it.
Therefore, we see that in free market, even the most ideal circumstances dont enable any reduction in prices in the long run.
Average prices always must go up because every seller works to have demand for his product greater than its supply.