mwave offers the Bionaire Warm Mist Humidifier, model no. BWM2601-U, for $45.99 plus $2.99 for shipping. (The Nerds via Amazon sells it for the same price.) That's the lowest total price we could find by $6, outside of the price below. It features tip over protection, auto shut-off, manual user reset, and more.
A close price: ANTonline sells it for $49.96 with free shipping.