son muy caras

they are very expensive

→ ser
phrase Rare #44,865
they are very expensive Used for feminine plural nouns; caras agrees with the nouns being described. Depending on context, it can also suggest that someone or something is costly or high-maintenance.
SP: Estas entradas son muy caras.
EN: These tickets are very expensive.

Estas corbatas son muy caras.

These ties are very expensive.

Las mujeres son muy caras, ya lo verás.

Women are very expensive, you'll see.

— Adiós, muchachos (1987)

Son muy caras.

They are very expensive.

— Haz lo que debas (1989)

Las frambuesas son muy caras.

Raspberries are very expensive.