LightInTheBox offers the Men's 26" 24-Speed Mountain Bike in Black or Yellow for $349.99. Coupon code "S4946932BIKE" drops it to $299.99. With free shipping, that's $400 off and the lowest price we could find. It features an aluminum alloy frame, Shimano shifter and derailleur, and double disc brakes.

Note: Uncheck "Add Shipping Insurance to your order" during checkout to remove the $6.99 fee.