The prices for ThermoSpas hot tubs range widely from $4,000 up to $22,000, depending on how many features you add to the model you choose. Given the average price of an acrylic hot tub is between $11,000 and $16,000, ThermoSpas keeps prices low by selling directly to customers instead of to retailers who then mark up the price before selling. Keep in mind the price of a hot tub includes maintenance and energy used over the years.