Seeing how hungry Saruman was for a Golden Fruit, Sheyan could not help but feel some regret. He guessed that if he could offer a Golden Fruit to Saruman, then there should be a follow-up mission, and the reward of the follow-up mission should be quite generous. Sheyan noticed that Saruman only offered the Golden Fruit mission after obtaining Elrond's Illusion Bone Crystals. Maybe a Golden Fruit was required to activate the crystals! It's hard to know which one's the cause and which one's the effect.
However, for Sheyan, the rewards he missed out on was not important anymore. The most important thing was the four Golden Fruits absorbed by the 'Stairway of the Sun', and the evolved ability 'Poison Monarch : Beast of Corrosion'. It's obvious that this ability was at least S-grade.