Answer:
Cien mil dólares.
Explanation:
The word caro means expensive in English, so you have to indicate the most expensive price. If you write each price in numbers you have:
cien mil dólares
: $100,000
dos mil dólares
: $2,000
cincuenta mil dólares
: $50,000
veinte y cinco mil dólares: $25,000
According to this, the most expensive price is cien mil dólares.