Actually, factory sealed boxes are quite consistent…12 holos in the 36 total. I’ve opened many;)
Is it possible to weigh other packs, too? If so, buying spare boosters would always be a risk :X
Also, is the difference in weight that much between a holo and a non-holo? Must be like 0.0001g 
It’s possible to weigh most boosters. There actually is a significant difference in weights in the new sets. I broke down and weighted one of my Dragons Exalted boxes and opened all of the packs to see if the weights were consistent. There is a difference between packs with a non-holo rare, a holo rare and a secret rare/EX/shiny. It’s enough for my 0.001g scale to measure. 