曼昆提出了之前我没有意识到的两点，一是数字教科书虽然比实体教科书便宜，

Mankiw raised two points that I didn't realize before. First, although digital textbooks are cheaper than physical textbooks, there is no way to sell them. This makes digital textbooks look less expensive. The second is that the additional functions of digital textbooks have costs, and these costs are included in the price of textbooks, and are ultimately paid by students. So digital textbooks are indeed more convenient than traditional textbooks, but they may not have a great advantage in terms of the prices students pay.

Mancune made two things I didn't realize before, one being that digital textbooks, though cheaper than physical textbooks, have no way to sell them, making them look less cheap. Second, the additional functions of digital textbooks are costly, and these costs are included in the textbook price, and ultimately paid by students. Therefore, digital textbooks are indeed more convenient than traditional textbooks, but in the price paid by students, there may not be a great advantage.

Mankiw put forward two points I didn't realize before. First, although digital textbooks are cheaper than physical textbooks, there is no way to sell them, which makes digital textbooks look less cheap. Second, the additional functions of digital textbooks have costs, which are included in the price of textbooks and finally paid by students. So digital textbooks are indeed more convenient than traditional textbooks, but they may not have a great advantage in the price students pay.