Amazon is offering some discounts on its Kindle line of e-readers. The online retail giant has started a promotion that offers customers the opportunity to get up to $50 off its line of Kindle, Kindle Paperwhite, Kindle Voyage, and Kindle for Kids Bundles. Those who opt for a standard Kindle e-reader, for instance, can now buy it for $50, a $30 savings on its regular $80 price tag.