I think this is one of those key + haunted headwears, several people would be more than happy to do 2-3 keys for a haunted spy set if they had no other options available. I think it's safe to assume that the hat carries the bulk portion of the set price.

Just because you can't get one for that price doesn't mean it's worth that much. Probably only applies to Halloween costumes though

Haunted collector logic: Why would I settle for 3.66 ref when I could get 5 keys by forcing someone to buy the whole set?