you don't want to weigh ONE of each as you want to know the mean or median weight of all your pre- and post- and during-oil crisis vinyl pressings and your varying thickness CD booklets. Also, older jewelcases are about double the weight of more recent ones. What about digipacs? Maybe David Ayers can get up from his chair and place some on his kitchen scales, while MikeWeil goes looking for his bathroom scales, wherever he hid those...
BTW, one CD cum jewelcase really does weigh about 100 grams, give or take 10 grams and a CD cum slimcase really does weigh about 50 grams. A single LP on average really does weigh 200-300 grams, depending on vinyl thickness and cardboard stock.
I didn't make that shite up!