Just had this happen again (XB-NA): I'll look at a master writ which advertises a certain reward - in this case 67 vouchers. But when I complete and turn in the item, I get fewer vouchers - in this case only 64. I've had this happen with less valuable master writs (7 offered, 6 given) and more valuable ones as well.
What gives?
I know the reward is in some way based on the components required to make the item; does the display of the actual writ calculate things slightly differently to the actual reward, or is there some hidden penalty system at work? In the cases I can remember, either it took quite a while to actually complete the writ once accepted (due to having to learn a trait), or I crafted the item at one of my Guild's crafting stations rather than travel to the zone - does that affect things?