There is only one direct flight operating from Islamabad to Beijing on each Thursday and Sunday. And the return flight from Beijing to Islamabad is available on each Monday and Friday. As for the tickets price, you could make an online enquiry on the page below with your specific departure and return date. https://www.travelchinaguide.com/china-flights/cheap-beijing-flights.htm Or, you could contact some booking agencies in Islamabad for the tickets reservation.