This deal has ended.
Overstock drops the Slumber Solutions Highloft Supreme 4" Mattress Foam Topper to $74.99. Better yet, activate this link to bag free shipping, making this just $2 above the all time low. It's available in sizes from Twin to California King for this same price. It is well reviewed with 4.5 out of 5 stars from over 300 happy buyers. There is no sales tax (except UT).