Ok the 2003 average wages were (according to the National Census):
Montana: 34,375 USD
Wyoming: 41501 USD
Virginia: 52,587 USD
Given the 2.3% national growth we have the following, assuming wages grew at least as much as inflation:
Montana: 35,165 USD
Wyoming: 42,455 USD
Virginia: 53,796 USD
Now lets say that we have a family in each state that uses 10 gallons of gas per week or 520 gallons per year.
Montana will shell out 1097$ or about 3.11% of their wages per year.
Wyoming will shell out 1029$ or about 2.42% of their wages per year.
Virginia will shell out 941$ or about 1.74% of their wages per year.
Ok, yeah, looks like either a vast shortage of refineries is to blame, or being the 41st in income and yet being almost #1 in tourism helps to keep Montanan's with less in their pockets than others.