勿吝高賢 Do Not Withhold Your Wisdom
如今君臣后妃，髮都剃落了，望老師勿吝高賢，願為門下。」八戒聽言，呵呵大笑道：「既要拜為門徒，有何贄見之禮？」如今君臣后妃，发都剃落了，望老师勿吝高贤，愿为门下。」八戒听言，呵呵大笑道：「既要拜为门徒，有何贽见之礼？」
逐句解 Line by line
Now ruler, ministers, consorts and queens have all had their hair shaved away. I beg you, Master, do not withhold your high wisdom, and let us become your disciples."
In 剃落 the 落 is luò, to come away or fall off, not the là of leaving something behind by mistake. 門下 — beneath the gate — is the ordinary word for a disciple's standing, and it is worth noticing who says it: the king is asking to be admitted to somebody's household.
Hearing this, Bajie laughed aloud. "If you mean to bow to us as disciples, what gift do you bring for the first meeting?"
贄見之禮 is the present a student brings on first meeting a teacher, a Confucian courtesy old enough to be set down in the Book of Rites. Bajie has correctly identified that a formal relationship is being proposed and has gone straight to the fee schedule.
Pilgrim's one instruction in the chest was that Bajie should not argue. He does not argue. He invoices.
The joke is sharper for being technically correct. A first-meeting gift really is owed, and any Ming reader would have known it. Bajie is not inventing a shakedown; he is enforcing the ritual, which is somehow worse.