Quest rewards and difficulty
Have you ever sat back and looked at the zenny reward for quest completion and compared them? It may be how the developers viewed the difficulty of each quest and I find that quite interesting. Example: A Tragedy in Silver and Gold has a 57300z reward while the highest zenny reward for any EX is 53400z (Bloodbath)
But in the same breath there are plenty of quests that don't line up with that logic as well.
Example: Redhelm EX has a reward of 31200z while a hyper G4 Deviljho nets you 32400z not a terrible comparison until you realize Ahtal-Ka urgent gives 37800z.
I don't think it's as simple as more money equals more difficulty. There's probably a multitude of factors that formulate the actual answer. Such as: Multiple monsters, hyper, being an urgent quest, elder dragon, location, health/damage modifiers and rank. I think it's something to keep your eye on. What do you think?