But this leaves out the old addage that "time is money".
I know for me, vacation time from work--as well as time that I'm not able to spend doing a few hours of "self-employed" activities-- is a huge factor in the decision.
For me, flying means about half a day (total) on each end of the trip, whereas driving would be a full two days, and leave me feeling pretty tired after.
There's no doubt that the "time is money" thing
can play a part. In my case, we'll be leaving mid-week & using all of the following week. Any overtime I work that partial week (and if our projections are correct, I will be LOADED UP come June) will come back to me as straight time. So, I lose that. People who have limited vacation time or are self-employed, also a factor.
On the flip side, what do most folks do with that extra time that flying affords them? Do they wait until Saturday night or Sunday to leave home? No, typically they fly out Friday night or first thing Saturday and wind up spending an extra day or two at their destination which obviously is a more expensive place to be than out on the road. So, the numbers can be tweaked any number of ways
You also have to factor in HOW you travel in a car. Do you get 30 MPG or 20 MPG, or even worse? Will you stay in a nice hotel on the way down, or the Super 8? Will you pack a lunch or pull into a restaurant for every meal? Is 1,000 miles from YOUR home comparable to 1,000 miles from someone else's? Maybe not.
Flip side of all that - what's your airport situation like? Will you have to make 1 or more connections or can you do a non-stop? Does driving to the airport require you to first start out driving in the opposite direction as you destination or is it "on the way"? Are you flying out of a major hub with reasonable airfare, or some little 7-gate miniport with no good fares?
Does your history of business travel mean you'll get free airline tickets? Or, does your CC rewards program mean you can have free hotels on your drive?
And there IS a line out there where it sort of becomes too far to drive in a reasonable amount of time (see the Portland to WDW thread for that!). Mapquest shows ~1,000 miles for us. That's not 2 full days, but rather 1 full day + 1 morning. As mentioned, figure on losing 1/2 a day to flying if you can get a non-stop (we can) and don't have to drive out of the way (we don't). Essentially, I'm losing 1 day in each direction compared to flying, as opposed to 2 days each direction for folks who live another 4-500+ miles further away. The other option for us, is to make it 2
very easy days with a stop in Chattanooga to see the aquarium on the way down & the one in Atlanta on the way back. Either way, no real exhaustion like there is if you're leaving at 4:00 a.m. and driving until 11:00 p.m. for 2 or more consecutive days.
So yeah, the equation - be it time or money related, or some combination of the two - is obviously different for everyone.
Speaking in general terms though, the more people you take with you, the more sense it makes to drive.