Walmart discounts a selection of Spa Sensations 6" Memory Foam Mattresses, with prices as listed below. That's at least $54 off list and the lowest total price we could find. It features a top memory foam layer and high density foam base layer. The sizes, each available with free shipping:

• Twin for $95 (a low by $32)
• Twin XL for $99 (a low by $45)
• Full for $105 (a low by $43)
• Queen for $125 (a low by $48)
• King for $145 ($54 off)