There are a lot debates in this board about the sales of Lumia 920/920T in China. It is really hard to know the exact number. In my previous post, I gave you the sale number in Tmall, one of the three major online distributors of Lumia 920/920T. But most of Chinese still prefer to buy the expensive cellphone from the real store, so that number can not really reflect the true sale number. if you check the sale number of iphone 5 from the same website, it was about 2K, and iphone 4 was about 1.5K last month. So Lumia 920/920T 2K sales from Tmall does not seem to be bad to me.
I tried to dig this thing more from a different angle. I found that the protection cases from Lumia 920/920T sold about 36K total. I guess it is reasonable to assume people buy the case only after they purchased the phone, and there will be more people to buy the case instead of phone online. But remember, the cases could be purchased from many stores, so it is reasonable to believe that sales of Lumia 920/920T should be much higher than 36K.
There's logic to your breakdown of the data. 36,000 cases is still not a lot of cases. Even if we multiplied that number on the order of ten we'd still have less than half a million. Nokia needs to be seilling millions of phones to turn in the numbers needed.
As I stated in the original post, Tmall is only one of the online stores to sell the cases. I bet there are more than 10 such stores, then you count numberous local stores. In my humble opinion, factor 10 is underestimated.