Get this Slumber Solutions 4" Highloft Supreme Memory Foam Mattress Topper from $53.99 at the Semi-Annual White Sale at Overstock. The Twin drops from $59.99 to $53.99, Full drops from $74.99 to $67.49, Queen drops from $89.99 to $80.99, and King or Cal King drops from $99.99 to $89.99. This is the lowest price we found for any similar 4" memory foam, and it only drops to this price on Overstock a few times a year (in November, the Queen size was going for $160 on Amazon). Also, check out the 4.5 out of 5 star rating by over 2900 reviewers! It also comes in a 3" version from $45. There is no sales tax (except UT).