* For "expensive": 비싸다 (bissada) is the most common way to say something is expensive.
* For "beloved/precious": This requires more context. You'd need to specify *what* is beloved/precious. For example:
* Beloved person: 소중한 사람 (sojunghan saram) - precious person
* Precious thing: 소중한 물건 (sojunghan mulgeon) - precious thing
* Beloved memory: 소중한 추억 (sojunghan chueok) - precious memory
Therefore, to get an accurate translation, please provide the sentence containing "mahal na."