He has his people inventory the Fey equipment that you bring back. As best the taffers and you calculate, the swarms killed 140 fey. Add that to the several you killed when you arrived back in Cheadsolas.
Only magical items survived the swarms, that and bones, although barely the bones.
9 Magic items are counted. Further analysis tells Ellic and others that there were more (potions and such) as there are lingering magical auras. However, the swarms destroyed as much as you found.
Ellic says, "You took the risk, so you keep any that you can use. I would ask that you donate those that you can't to the war effort."