Well although carnival is 3.5LV6 and CBU, it attracts ONLY 68% duties because of 11 seats configuration and imported under commerical scheme. All vehicles under commercial heading have much lower custom duties and that is why one can import a Hiace, otherwise it would have been way way more.
Keep in mind the Carnival was introduced [ the discontinued gen] at mid 4 million and top varaint also near 5 Million.
Import a 8 seater or any other seats configuration below 11 means over 400% in duties with 3.5L engine. Sorento will be below Carnival as far as price but not significantly.