The only cartels that have lasted have been government cartels. There is no essential difference between a cartel and an ordinary corporation or partnership. Not even the De Beers cartel is all powerful.

Price is determined by the equilibrium price and the equilibrium quantity. If your good is not selling, you lower the price. If your goods fly off the shelves you are selling too cheaply and you raise prices.

Microeconomics is concerned with the actions of individuals. The focus of macroeconomics is entire sectors of the economy.

Why is it that things like bread and water which have high use values are cheap while on the other hand luxury items like diamonds are very expensive? This paradox was not solved until it became understood that people choose only a marginal unit - this loaf or this diamond.