Its probably more because the fight with the dragon damaged it so much that there are only a few usable scales remaining. I would argue a GM could allow more with a survival check to see if you could scavenge some more.
Good point. Next time we use save or die affect successfully on a dragon I'm going to bring that up.
*shrugs* They don't want to hand out too much free crafting material on dragons on top of their loot?
BINGO