```select c.cust_name, ois.total_price
from Customers c join Orders o on c.cust_id = o.cust_id
join (select order_num, sum(item_price * quantity) as total_price
       from OrderItems
      group by order_num
     ) as ois
     on o.order_num = ois.order_num
     where ois.total_price > 1000