because all the transaction are between limited address out of a HUGE set, at-least that part can be compressed
Do you know how compression works? If not, try to put some bitcoin addresses into a file (in binary form of course) and compress them with zip or whatever, then check results.
I think you don't understand compression, I already indicated bit-coin addresses and part of signed transactions being random, what I was talking about the address occurring multiple times in block chain.
e.g. a very sketchy compression of a simplest blockchain
14x999VDuEd48ykqYrg8K6a1kto45a3BHf => 1HQ3Go3ggs8pFnXuHVHRytPCq5fGG8Hbhx
1C8ToSDT9dwxy7uXmU5AXpx1oXbV84GwpN => 1HQ3Go3ggs8pFnXuHVHRytPCq5fGG8Hbhx
1MZqmDHxyW4htFaZFsQ5q78i9nL3r99BtW =>1C8ToSDT9dwxy7uXmU5AXpx1oXbV84GwpN
can be compressed to
a=14x999VDuEd48ykqYrg8K6a1kto45a3BHf
b=1HQ3Go3ggs8pFnXuHVHRytPCq5fGG8Hbhx
c=1MZqmDHxyW4htFaZFsQ5q78i9nL3r99BtW
d=1C8ToSDT9dwxy7uXmU5AXpx1oXbV84GwpN
a=>b
d=>b
c=>d