The 8" Slumber 1 Mattress-in-a-Box falls from $149 to $109 for Twin, $159 to $159 for Full, $209 to $174 for Queen, and $249 to $214 for King at Walmart.com. Plus, shipping is free. We found every size going for over $200 elsewhere, and this is one of their best-selling mattress every year with 4.5 out of 5 stars based on 6,009 reviews! Sales tax is charged in most states.