A full suit of plate armor, that is, plates of steel covering almost the entire body of the Knight and his horse, could cost as much as a small farm during the Middle Ages.
The horse itself would cost the same amount, in today’s money, as a luxury car.
Much like playing polo and collecting Swiss bank accounts, being a knight back then was reserved for only the wealthiest of sons.
Being competent wasn’t good enough, you had to have the funding and wealth to afford to be a Knight back then.