還省柴 Boiling Him Saves Firewood
又一個說：「煮了吃，還省柴。」又一個道：「他本是個稀奇之物，還著些鹽兒醃醃，吃得長久。」行者在那梁中聽見，心中大怒道：「我師父與你有甚毒情，這般算計吃他？」又一个说：「煮了吃，还省柴。」又一个道：「他本是个稀奇之物，还着些盐儿腌腌，吃得长久。」行者在那梁中听见，心中大怒道：「我师父与你有甚毒情，这般算计吃他？」
逐句解 Line by line
Another said, "Boiling him saves firewood."
Ten characters, and the argument has reached economics. 省 is shěng, to save or economise — the chapter's only occurrence of this character, and it is being used to make a point about fuel.
Another said, "He is a rare article after all. Put some salt on him and cure him and he will keep a long time."
著些鹽兒 takes 著 as zhuó, to apply — one of only three places in the chapter that reading is right. 吃得長久 again takes 長 as cháng for duration. The proposal is to treat him as preserved stock, which is exactly what the strips drying in the sun outside already are.
Pilgrim, hearing this from up in the beams, was greatly enraged in his heart and said, "What deadly grudge has my master with you, that you should plot to eat him like this?"
中 appears twice in this line at its ordinary reading, inside the beams and inside the heart, against the four places in this chapter where the same character means struck by something. 甚 is shén, what — Wukong's question is rhetorical and it is also, for him, a real one.
Four fiends, four proposals: fry, steam, boil, cure. It is a genuine culinary discussion with genuine trade-offs — flavour against fuel against shelf life — and the subject of it is tied to a tree in the garden.
Wukong's fury takes an odd shape. He does not ask how they dare; he asks what grudge they have. He is looking for a motive, and there is not one. They want to eat his teacher because eating him is useful, and that is all.