Question: I submitted a mistake about the road sign at the end of the film that shows how many miles to Chicago and that there would not be such a sign in Vegas. My question is what was the point of adding that into film? And also I think it is safe to assume that the Griswolds booked a flight back to Chicago (round trip). If they did it doesn't seem like they would've had time to cancel it since they didn't know until the end that Rusty won the 4 cars. So wouldn't they have lost more money that way as well?
Answer: A sign saying how many miles home is a common film making technique. It's not meant to be realistic. Considering the Griswolds won enough at keno to recover their losses and at least $120,000 worth of cars, I can't see them getting too upset over the airfare which is likely less than a thousand dollars.
So they did turn in the ticket and got the money? I know they drove off in the cars Russ won.
No, Clark cashed the tickets in to keep gambling.
Answer: They live in Chicago. I think it was just a nod to the number of miles and who knows what could happen to them on the way home.
Answer: Don't forget that Clark gambled away their plane tickets. He needs to drive the 4 new cars Rusty won to Chicago.
Answer: Clark sold the plane tickets to continue gambling.