Hainan Airlines, a 5 star airline is offering return flights to Hangzhou (HGH) from Sydney for $292 and Melbourne for $319 (or $336 with 1 night hotel stay in Xi'an). Also on sale is Melbourne to Shenzhen for $297 including a 1 night hotel stay in Xi'an. Flights connect through either Changsha or Xi'an (free stopover city). Two checked bags and meals are included. Similar to last month's Hainan deal to Shanghai/Beijing with a hotel stay. A hotel is provided when stopovers are greater than 6 hours.
Melbourne - Shenzhen $297 Includes 1 night hotel. $333 booked direct from Hainan. So basically fly into Xi'an at 5:45PM, check out the city, fly out in the morning onto Shenzhen.
Sydney - Hangzhou $292 or $326 booked directly with Hainan.
Melbourne - Hangzhou $319 or $336 with 1nt hotel or $353 booked directly with Hainan.
Melbourne - Beijing $336 Skyscanner - $354 if booked directly, $319 with no free hotel
I don't know too much about Hangzhou other than it's a popular tourist destination near lakes and is about an hour away by train from Shanghai. Guide. There may be some dates that align to get you 2 nights hotel but I haven't found them. You'll have to keep manually plugging in dates as all of the sites don't seem to be properly pulling up the right prices.
Shenzhen has some awesome tech markets. Check out this guy creating an iPhone from scratch by buying parts from the markets.
More info about hotels and possibility of free hotel in Changsha
Hangzhou Tip Off Via Scott's Cheap Flights
Great find. Also as always, don't forget to add visa costs.