16 GB iPhone 5s are now $149.99 with a two-year contract while 32 GB models are $249.99 on their online store. There were a round of discounts on iPhone 5 from various retailers, including Best Buy, just a couple days ago but this looks to be the largest discount the product has seen so far.
It doesn't appear to be possible to take advantage of the $50 discount while also receiving a $25 gift card and there's no indication how long this deal will last.
Update: Dealnews notes that Best Buy is now offering the $50 discount with 5,000 Reward Zone points (equivalent to a $100 Best Buy gift card) on the 16, 32, and 64GB iPhone 5 models. Free shipping, online orders only.