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.
More details at the link below...