Prices can range greatly from about $399 into the thousands for a King Mattress set. However, one of the greatest mistakes here would be “penny-pinching.” This investment is a serious one that can greatly affect you and your life. The Better Sleep Council recommends that you buy the very best mattress that you can reasonably afford. If we actually spend approximately one-third of our lives in bed then your investment will cost you only “pennies” each night over the next ten years. So, if you were to spend $2,000 on a King Mattress Set, it would cost you around 55 cents a night over the next ten years.