They are also sold in JD.COM. It seems that JD.COM is currently competing with Dangdang, and it is a price war.
If you want to know which bookstore sells the lowest book you want, and you don't want to go door to door, I recommend a website for you. Baidu "Drunk Taobao" ranked second.
Searching on this website will show which bookstore has the lowest price. If you want to buy a lot of books, put the books you want to buy in the shopping cart, and then compare them in the shopping cart to find out which bookstore is the cheapest to buy all the books.