Target offers the Coleman Lay-Z-Spa Inflatable Hot Tub for $349.99. Coupon code "TGRDZRHP" cuts it to $344.99. With free shipping, that's the lowest total price we could find by $25, outside of the mention below. It measures 71" x 71" x 26 and features 120 jets, a chemical floater, and two filter cartridges.
A close price: Pool Supply World has it for $349.99 with free shipping. (Note that new customers can apply "SAVESFIVE" to match Targets price above.)