Your example with cocaine is a good one, people caught with cocaine aren't carrying pure cocaine either. They are usually charged with the weight of the cutting agent as well, which in my view is equally stupid. If you have a pound of baking soda with 1gm of cocaine mixed in it, you shouldn't be charged with having a pound of cocaine.
I'm not saying it can't happen, its just not very common. The culture where acid is prevalent is much more communal.
According, to the studies shown here on erowid, the blotter tabs examined by labs since '97 range anywhere from 19 micrograms all the way up to 148 micrograms. The older lab tests from the 70s and 80s seem to have a greater range testing at anywhere from 5 micrograms to 500 micrograms per tab!
All of these blotter tabs are going to weigh roughly the same amount. Some of the weaker ones may even weigh more than the stronger ones due to the difference in the type of paper.
This is not true. I can take a clean sheet of paper and dissolve as much LSD (or as little) on it as desired. 1g of near-pure crystal will definitely contain thousands of doses. 1g of paper could contain anything from 0, 1, 10, or 100 doses or more.