Charlie is fascinated with what's inside the jar and offers at first $12.00 to carnival barker (Billy Barty). At that point, Charlie finds an extra quarter in his pocket and the barker agrees to sell the jar for $12.25. On the closeup of Charlie paying the barker, he puts 1 five-dollar bill, folded in half, 5 one-dollar bills, and one quarter onto the carnival barker's table which totals only $10.25.
Charlie carries on the back of his truck - unsecured - a single, 50-pound bag of all-purpose flour. A load such as that could easily fall off when it could just as easily be put in the cab.