At Dick's Sporting Goods, buy a pair of Nike's Men's or Women's Slides and get 50% off a second pair. With free shipping, many are at the lowest total prices we could find if you're buying two pair. Sales tax is added where applicable.
For example, buy two pairs of Nike Men's Rejuven8 Slide 3 Slides in Black/White (pictured) for $29.95. With free shipping, that's $20 under the lowest total price we could find for two pairs elsewhere. They're available in sizes 6 to 15.