Zappos lets you return what you bought and gives you a full refund--including all shipping costs--regardless of whether you purchase a replacement item.

FORBES: Magazine Article

Failed deliveries are also more expensive for online retailers because those consumers are more likely to call customer service, switch to a competitor, or get a replacement item.

WSJ: Amazon's New Secret Weapon: Delivery Lockers

By contrast, online retailer Lands' End will pay for the shipping on a replacement order, but if you don't want to replace the item, it won't refund your original purchase.

FORBES: Magazine Article