Boost Mobile is offering $200 off the iPhone 5s and iPhone 5c if you switch to Boost from another carrier.
The carrier lists both devices for $100 off Apple's retail price; however, until November 24th a special promotion is giving an additional $100 off to switchers.
9to5Mac confirmed the deal with a PR rep who said:
Yes. Now through Nov. 24 new customers who come into a participating Boost Mobile store and switch to Boost Mobile from another carrier will be eligible for a special in-store promotion of $100 off any device bringing new customers additional cost savings. The link below will help consumers find participating stores in their area that are selling iPhone.