I think this is an unanswerable question. You won't save much by doing this and it'll involve a lot of hassle. If you really want to go to multiple shops and barter.
www.taobao.com
OR
The Zhong Guang Cun disctrict in north Beijing.
They got everything you'd ever need....lowest price on a iPhone in Beijing is 3500RMB with receipt 3000RMB for one without a receipt.
But I guess receipts wont do you any good if it's broken anyway ... no service points around.