what is the advantage of the 'group buy'? - is it to save on shipping to usa? or we get additional discounts?
As said on the
BTCC Storepage, they do not currently sell to US residents whatsoever. If you want to buy something from BTCC and you live in the US, something similar to this is the only way you can do so.
Any items ordered will be shipped to someone else outside of the US initially, then reshipped to the US where they will be distributed to everyone who ordered.