Some companies have cooperative relations with the book building. Every year, these companies get or spend a certain amount of money to buy library cards in the book building, and then give them to employees or formally buy books.

These books and cards themselves have a face value of several hundred yuan, and most of them are distributed to employees free of charge, and then the employees sell them to the "payer" at a price lower than the face value.

At the same time, these books cards also enjoy a 20% discount (maybe this discount, I can't remember the specific discount).

For example, if you buy a book with 100, you need to pay 100 if you pay for it yourself. Even if you have a membership card, it will be 15% off or 10% off at most. If you ask donors to pay for you, they can give you a 20% discount on the card and then charge you a 15% discount to earn a difference of 0.5%. It's good for you and the donor.