But no one uses the price of the transaction between you and your friend as a reference. If the exchanges, whose prices are used by the indexes of the most ranking sites, are not working, the main price indicators will not be working either.
True. I was simply illustrating a point that this question has no definite answer. Lets put it this way then - suddenly everyone in the world decides they don't want to sell bitcoin, and everyone is just holding. I come along and say I will sell 1 bit for 1 cent. Someone snaps up my offer, and then everyone in the world goes back to holding. The price of bitcoin is now $10,000.
You can take this to the other extreme and say ($10,000 - $3,468 (current price))*17,519,462 (circulating supply) = $114.4 billion is needed to reach a price of $10,000 if every bitcoin is sold to get there.
The answer obviously lies between these two numbers, but where exactly, no one can say.