If you really want to see the math broken down, I'll do my best:
Let's say, for arguments sake, that you have two crystals: Lavender at 95% pure and Needlepoint at 100% pure (again, this is for arguments sake, as I think all crystals are above 95% pure, thereby making purity useless):
You have a 1 gram crystal of each. That means 1,000,000 ug of base weight. If your lavender crystal is only 95% pure, that means there are 950,000ug of pure 100% el, and 50,000ug of impurities/byproducts from the synthesis. Now, 1 gram of crystal will lay (10) tenpacks. A tenpack is ten sheets (10,000 doses in total). Now if you take the amount of pure el, and divide it over the amount of hits (to get a ug per hit amount) you would get: 950,000ug/10,000 hits which equals 95ug per hit.
Now if you have your needlepoint crystal, 1 gram as well. That means 1,000,000ug of base weight. But since your crystal is 100% pure, you get 1,000,000ug of pure el and 0 ug of impurities/byproducts. Again, going with 10,000 doses per gram crystal, you get 1,000,000ug/10,000 hits which equals 100ug per hit.
Now do you think you'd really be able to tell the difference between 95ug and 1000ug?
The reason I used such high numbers is because it is nearly impossible to get a lower quality potency. Going back to high school chemistry class, let's take a look at crystallization. If one gets to the last step in el production, it is taking an aqueous solution containing el, as well as the solvent in which the crystals will form. Solvents used are those that have quick rates of evaporation. Now if one takes their aqueous solution, and evaporates out all the solvent, they are left with crystals. If not all the solvent is evaporated, you would be left with some of it in the crystal (there is your "impurities/byproducts"). When crystallization happens, one should be left with nothing but crystals, and no solvent.
Again, I will repeat myself, this is only how I understand it. I would love to hear some input on how other people believe it is created/laid/synthesized. Happy trails.