Walmart offers the Spa Sensations 12" Theratouch Memory Foam King Mattress in White for $289 with free shipping. That's $10 under last June's mention, a low by $69, and the best price we've seen. It features 3" of Theratouch premium memory foam, 3" of ventilated air-cool foam, and 6" of high-density support foam.
They also have it in Queen for $269 with free shipping. That's tied with last June's mention and the lowest price we could find by $51.