If you want to get the longest lifespan out of your mattress, you would be wise to spend at least $800 on a good mattress. Otherwise, you won't get a good night's sleep—cheap mattress=lumpy mattress—and sooner rather than later you'll have to spend your hard-earned money to buy a new mattress set all over again. Besides, the average person spends one-third of a lifetime sleeping. Doesn't it make sense to sleep on the best bed possible?