This best-selling 8" Spa Sensations Memory Foam Mattress drops as low as $129 at Walmart.com. Plus, shipping is free. This is the lowest price we've seen to date on the Twin and Queen sizes, and over 4,200 reviewers have given it a perfect 5 out of 5 star rating! The Twin size drops from $149 to $129, the Full size drops from $199 to $169, Queen drops from $239 to $189 (it's going for $255 at Amazon), and King and Cali King drop from $259 to $199. Sales tax is charged in most states.