i've seen some on Craigslist (locally) go for as low as $350 in north carolina--i'd suggest that as opposed to ebay b/c you can meet to purchase.
but that doesn't necessarily mean that it will be coverable by warranty under Sprint
Its going to be hard to find it too discounted as its still very popular and in short supply. Theres not too much incentive to discount it when just having it in stock will get it to sell.