For its members, Sam's Club offers the Serta Perfect Sleeper Castleview Cushion Firm Pillowtop Queen Mattress Set for $498 with free shipping. (Non-members pay $49.80 more, so it's best to buy a Sam's Club 1-Year Membership for $45 instead.) That's tied with our mention from a week ago and $202 under the lowest price we could find for a similar item sold elsewhere. It includes your choice of a 9" or 5.75" box spring.