You have to think more about gas when driving your own car:
1. The government reimberses 0.55 per mile for business purposes. Depending what you drive, that could be alot or it might not be enough. To dribe round trip 500 miles each way that would cost you about $550. I highly doubt a coach ticket would cost you that much.
2. Even if you are looking at just gas prices, your vehicle probably gets between 15 to 30 miles per gallon depending if you drive an SUV or hybrid. Maybe even less if you drive an old beater pick up. Average price of gas for AZ and CA lets say is $4.00 per gallon. So at those milage rates you end up paying betwenn about $130 to $270 for just gas. This does not include inurance, maintenance (i.e. oil changes, repairs, tires, breaks, etc.), registration, inspections, etc. So how much is it for a round trip ticket? I just found tickets for $85 or $170.