What is a reason that market prices are not always the same as the equilibrium prices?

A: Market prices are often set by buyers rather than sellers.
B: Supply and demand are not well-understood by business owners.
C: The equilibrium is not always the most profitable price point.
D: It is not always practical for businesses to change their prices on a daily basis in order to reflect the equilibrium price.

D: It is not always practical for businesses to change their prices on a daily basis in order to reflect the equilibrium price.