Have you ever seen anything come out of Hollywood that didn't have an agenda? Anything that was true? Anything that wasn't a commercial for some product? Wait, I bought it hook line and sinker.
1969 gas was 14.9 cents a gallon at the station on the corner 3 houses down from where I lived. I could fill the tank on my bike for 30 cents and the tank on Dads caddy for 5 bucks. As for the Hippys, ya gotta admit Free Love was not a bad thing.
Not only might gas be a problem, but you never once see any of them fixing anything on their panheads. Heck, they don't even put oil in them. A long trip like that and no wrenching? I don't think so.