I also drove to Vegas -- my mileage was 2,700 miles over three days. Cheapest gas I found was $3.67 and highest $5.24.
My guess for your contest:
Mileage -- 6,021 miles
Gas Prices -- $3.60 to $5.45
It was a beautiful drive across Texas, New Mexico, Arizona and Nevada. Only wish next time we don't encounter extremely strong winds through New Mexico and Arizona.
Thanks for the contest.