Air China flies from YVR via PEK to MEL, with a long stopover (8 hours or so , which is time to go visit Tiannamen square). Google flights is showing $4089 for a semi-random 5 day trip at the end of February. You could add YYZ-YVR in Econ and be well under budget.

CA flights accrue AP miles. They have a great hard product (lie flat beds) and I found the soft product pretty good when I did this route 15 months ago. The long stopover may be a good thing as I had read that CA aren't too supportive in the case or IRROPS so its nice to have a buffer against delays. You can get a visa on arrival in Beijing for stays of <24 hours (please check if rules have changed though)