Greenjia via Amazon offers Prime members the Choetech 6-Port Rapid USB Wall Charger for $19.99. Coupon code "H6DJVKSK" drops it to $17.99. With free shipping, that's the lowest total price we could find by $9. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $6.52.) It provies up to 50 watts (10 amps) of power with smart detection technology.