Whether the question is returns or something else. Few will open their wallet if they have doubt. Unlimited and free returns removed a large amount of doubt. If fact, as mentioned, it likely triggered more sales.
You'd have to spend a significant amount of marketing budget to get what Zappos did from their return policy and customer service. Those weren't expenses, they were investments.
That’s basically the business model of REI; they rarely have the best prices, but if something breaks they’ll make it right.