Have you noticed any changes lately with your Amazon Prime shopping routine? If you live near a Whole Foods, a Kohl’s or an Amazon Fresh grocery store, you might be incurring a one-dollar charge every time you drop off returns at a UPS Store. Conversely, Amazon might be offering you $10 discounts for skipping delivery and picking up a package yourself. The e-tailer has been testing various strategies to reduce delivery costs, and to see how far customers will go to save a buck or ten. And where Amazon leads, other retailers will surely follow.