isn't responsible to make sure you have the requirements unless agreed upon, you showed him your stats what does that prove? He can't know all the requirements for every quest, that is your responsibility before coming to the user asking him to do quests. I think you should still give the gp back, its 5.5m you agreed to do the quest, you didn't know requirements obviously, but thought he had them, so not sure why we are wasting time, you didn't do anything for the 5.5m so no time lost no money lost other than a big waste of time. At this time I can't force a refund, but lets hope @Gilgad does the right thing.
It seems you both probably did minimal research and thought the quest could be completed, a mistake on both parties involved IMO.