It took me a while to reproduce it.
It is very strange, the sql "SELECT o.*, o.created_on as order_created, u.*, s.order_status_name FROM #__virtuemart_orders o LEFT JOIN #__virtuemart_orderstates s ON s.order_status_code = o.order_status LEFT JOIN #__virtuemart_order_userinfos u ON u.virtuemart_order_id = o.virtuemart_order_id WHERE o.virtuemart_order_id=yourOrderId"
just returns a 99999.99999, the used database field has DECIMAL(10,2), so it is big enough. I am on it