Amazon offers Prime members the Madd Gear Alloy Folding Scooter in Black for $13.71 with free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, shipping costs $5.58.) That's the lowest total price we could find by $21. It features an adjustable handle bar, aluminum deck, and 100mm PU wheels.

Update: The price has increased to $16.45.