"Sunt scumpi sau ieftini?"
Translation:Are they expensive or cheap?
Indeed, the verb "a fi" has the same conjugation for first person singular and third person plural:
However, in this particular example, both adjectives end in an "-i" that marks the plural.
Though it is true that, for adjectives with no plural form, you could translate to both:
Sunt maro. - They are brown.
Sunt maro. - I am brown.