Sam's Club offers its members the Serta SleepToGo 12" Gel Memory Foam Luxury Queen Mattress for $399.98 with free shipping. (Non-members pay $499.98 plus a $50 surcharge, so it's better to purchase a 1-Year Sam's Club membership for $45.) That's tied with our December mention and the lowest price we could find by $48. It features three layers of foam for pressure-relieving support.

It's also available in King for $499.98 with free shipping. (Non-members pay $160 more.) That's the lowest price we could find by $400. Both deals end March 25.