How did gertrude stein characterize her fellow writers in the 1920s?

Stein referred to them as "The Lost Generation."

World War I and the aftermath of the war is what gave them a feeling of lostness.  The Lost Generation was affected by disillusionment by those came of age during the war years, and began to question traditional values.  Some of the writers of the "Lost Generation" were Ernest Hemingway, F. Scott Fitzgerald, and T. S. Eliot - along with Gertrude Stein herself.  

high entry costs prevent new producers from entering the market.

explanation:

an oligopoly is a term used to clarify the structure of a particular market, industry, or organization. a market is considered oligopolistic or amazingly focused when it is shared between a few companies.