Barriers high enough to create monopoly can be due to: (1) government blocking the entry of more than one firm into a market; (2) one firm having control over a necessary resource; (3) the existence of network externalities in supplying the good or service; (4) economies of scale so large that one firm has a natural monopoly.
We have considered how markets form in response to many factors, but really it comes down to companies selling products that people want and need to buy. If the product is carrots and just about anyone can grow them and loads of people want to buy them, then you have a perfectly competitive market like we saw in the farmer’s markets.
