With price fluctuations I'd go with weight.Yeah that would stink.
Heck there was even a guy who insured his cigars against fire damage and made a claim when they got damaged by being smoked. I forget the outcome of that case.
I wonder with pipe cellars if it would work better to insure for dollar value (which would be hard to prove), or weight and volume. Like it gets damaged and you get new tobacco to cover what you had.