While somewhat less convenient than the "official" event hotel (Hampton Inn), there are several less expensive lodging options available off I-40 south of RDU.
In particular, the Spring Hill Suites hotel, as part of a special Marriott promotion, has 2 and 3 bed (including one sofabed) suites for $55.20 (+7.59 tax) per night. It is 100% smoke free.
http://www.marriott.com/hotels/travel/rdush-spring...