What is the average cost of a king mattress?

A king mattress can range in price from $300 at Target to over $4000 at Raymour & Flanigan for example. There is no average price of a king mattress since the specifications for any mattress are wide and varied according to types of materials used and type of mattress period. Just like a car, you can buy a budget model or a luxury model according to your needs and wallet.