I find it highly unlikely that the Al Quida went around filming everything they did and that somewhere there's a cave full of tapes waiting to be discovered and sold. This stinks of just too coincidental IMO.
I don't. bin Laden's a megolamaniac and undoubtedly felt that he was (or is) the second coming of Mohammed. He had plenty of money, and plenty of buttboys who followed him around.
Why wouldn't he record his every move, and everything he did?
And, if some Afghan found or knew about the tapes, why wouldn't he hold out for some coin?