What's the cheapest flight to Beijing—and where can you buy the tickets?
Cheapest flights are currently around RMB500-600, which are usually the first flights early in the morning or the last flights late at night. Which airline and which specific flight is the cheapest depends on the day of departure and the day of booking.
Qunar has a chart of the flight prices Chengdu to Beijing
Tickets you can buy at most travel agencies or online on qunar.com or in English at http://english.ctrip.com and http://www.elong.net who may have additional promos for return flights.
No matter what Beijing flight you book and how much you spend be prepared for delays.