1) This book is the most expensive.

这本书最贵。
2) The price of this book is high.

这本书很贵。
3) Both books / Both the books / Both these books are expensive.

这两本书都很贵.
4) This book is a little expensive.

这本书有点贵。
5) This one is the most expensive.

这个最贵。
参考词条