At the end of (every? besides horn and hand) leve, there is a chest drop that may have equipment in it as well.
The "Reward" is only half of the reward.
Actually, now that you mentioned it.... I was helping my brother do a faction leve with onion Onion Patterns (boots) reward, and at the end of leve I got them in my loot list/inventory as well. Not sure if it's because his
reward was those boots, or if it was purely by chance.
Either way, 100 or 200 guild marks is too much for a random chance of an (usually average) item, in my opinion. Guild marks, as well as gil is easy to come by via regional leves as well, and mostly everything else can be crafted/bought from Wards.