SELECT 
    e.id,
    e.asset_id,
    (e.downtime_hours * e.prod_rate + e.parts_cost + e.labor_cost +
     e.env_cost + e.reg_cost + e.safety_cost) AS total_cost,
    e.occurred_on
FROM events e
WHERE e.occurred_on IS NOT NULL
ORDER BY total_cost DESC
LIMIT 10;