Using
http://beta.itasoftware.com (don't use Expedia or Travelocity), I'm pulling up $379.60 for this routing:
Norfolk, VA to Denver, CO: 1765 miles 6 hrs 3 min
US Airways Flight US975 on a Boeing 737 (jet) in coach class
Departs Norfolk, VA (ORF) Wed, Aug 4 11:30a 1 hr 3 min
Arrives Philadelphia, PA (PHL) 12:33p
Layover in Philadelphia 57 min
US Airways Flight US6273 on an Airbus A319 (jet) in coach class
(operated by United Airlines as Flight UA721)
(snack, movie)
Departs Philadelphia, PA (PHL) Wed, Aug 4 1:30p 4 hrs 3 min
Arrives Denver, CO (DEN) 3:33p
Note: You must change terminals in Philadelphia (PHL).
Denver, CO to Rapid City, SD: 300 miles 1 hr 20 min
United Airlines Flight UA6292 on an Embraer EMB-120 (prop plane) in coach class
(operated by UNITED EXPRESS/SKYWEST)
Departs Denver, CO (DEN) Tue, Aug 10 7:30a 1 hr 20 min
Arrives Rapid City, SD (RAP) 8:50a
Rapid City, SD to Norfolk, VA: 1922 miles 9 hrs 6 min
United Airlines Flight UA6735 on a Canadair Reg. Jet (jet) in coach class
(operated by UNITED EXPRESS/SKYWEST)
Departs Rapid City, SD (RAP) Wed, Aug 18 10:22a 1 hr 8 min
Arrives Denver, CO (DEN) 11:30a
Layover in Denver 2 hrs 50 min
US Airways Flight US120 on an Airbus A321 (jet) in coach class
(food for purchase)
Departs Denver, CO (DEN) Wed, Aug 18 2:20p 3 hrs 4 min
Arrives Charlotte, NC (CLT) 7:24p
Layover in Charlotte 51 min
US Airways Flight US690 on a Boeing 737 (jet) in coach class
Departs Charlotte, NC (CLT) Wed, Aug 18 8:15p 1 hr 13 min
Arrives Norfolk, VA (ORF) 9:28p
... which is somewhat closer to $300 than the Expedia fare you're pulling up.
There are a bunch of different routings to play around with. Good luck searching.
aloha