I just got the same email and I am pissed.   I paid them .39 BTC total for 3 units and they will not refund my .39 they will only give me todays exchange rate..

Now they want me to pay them another 6k to get the 821 units..   That is over triple the price I paid them for the original units yet not even double the hash power..   

In my eyes MinerWarez is a fraud point blank!!!!! 

I am going to tell them to refund my money and the next batch of miners I purchase will be 841s and directly from Canaan. Until the point that the 841 is released I will run what I have purchased from my unofficial vendor who in fact just got a shipment of 160 in yesterday.

For all those who feel the need to comment about the fact that I have purchased from an unofficial vendor save your breath and shove your comments..  Here is a photo of the units we picked up 10 days or so ago..

https://image.ibb.co/hhKK46/Miners_001.jpg