premium (n.)

c. 1600, "reward given for a specific act or a particular line of conduct," from Latin praemium "reward, profit derived from booty," from prae "before" (see pre-) + emere "to buy," originally "to take" (from PIE root *em- "to take, distribute").

The sense of "amount to be paid by agreement for a contract of insurance" is from 1660s, from Italian premio. The adjectival sense of "superior in quality" is first attested 1925, originally in reference to butter. Figurative use of the phrase at a premium "at more than the usual value" is by 1828.