Yeah its one of the dirty tricks in the game- WATER WEIGHT!
The best way to rehydrate super dry weed is with the tortilla method. Take a name brand tortilla, MUST HAVE PRESERVATIVES, and throw one into the bag with the weed- you can increase the weight by up to 10% overnight ;-)

Sneaky AF but you can do this with POUNDS and make some free weed, or extra cash, so this is what a lot of the bigger dudes end up doing sometimes (or the middle men they work with).