Sandufu The idiom "Luoyang paper is expensive" originally refers to the price increase of Luoyang paper due to the shortage of supply. Later, this idiom was used to describe the popularity of works and spread widely. From "Zuo Zhuan of the Book of Jin": "Therefore, luxury houses compete for writing, and Luoyang is expensive for paper." Zuo Si's "Sandu Fu" caused a great sensation in Luoyang at that time, and people spread it one after another, resulting in a shortage of paper in Luoyang and rising prices. Therefore, the idiom "Luoyang paper is expensive" has spread.