Walmart offers the Lava Lite 14.5" Classic Lava Lamp in Purple Wax/Blue Liquid, model no. 2118, for $9.97. (Amazon has it for the same price with free shipping for Prime members.) Opt for in-store pickup to avoid the $4.97 shipping charge. That's the lowest price we could find for any color by $2. This 20-oz. lamp features a chrome base and cap and requires one 25-watt bulb (included).
Also available is the Lava Lite 11.5" Accent Lava Lamp in Red Wax/Clear Liquid, model no. 1910, for $9.97 via in-store pickup. That's the best deal we could find for any color by $3. This 12-oz. lamp features a silver base and cap and requires a 15-watt bulb (included).