This Signature Sleep Memoir 12" Memory Foam Mattress in King Size drops from $369 to $349 at Walmart.com. Plus, it ships for free, making this the best price we could find on anything similar by $104! It is designed to meet the curves of your body, for better alignment and more restful sleep. It also has near-perfect reviews from 183 reviewers thus far. It is offered in Twin, Full and Queen as well, all of which are $20 off right now. Sales tax is charged in most states.