Why does a Starbucks coffeehouse face a downward-sloping demand curve while a dairy farmer has a horizontal demand curve? What other suppliers might face a downward-sloping demand curve?

How do barriers to entry impact the level of competitions in a market?What might happen to the market price as greater barriers to entry come into existence?

All barriers to entry are not created through market conditions. Barriers to entry, such as patents, licenses, or international trade restrictions, may be government imposed. How do government-imposed barriers such as patents impact consumers and suppliers in these markets?