Teng
10
Of course, 156 is an average value. The one we can expect. Not something that will actually happen in practice - in any case. 
In addition, it is not a fact that there is such a high probability of dropping a recipe in vaults.
I usually took parts of recipes from the mi-go dragonfly in the ruins northwest of the Tower. There, I estimated the probability of getting a recipe at 15-20%. And in vaults, IMHO, less.