Mt. Gox had most of the transactions, value was defined by supposed offer and demand over there.
However Mt. Gox was a fraud, a ponzi and due to the previous two characteristics: a fictional market.
We don't have any idea of the real market value.
I know what you're getting at, but the fact of the matter is Gox didn't have MOST of the transactions
for a while...they used to be the biggest years ago, then they declined, and now they are bankrupt.
Over the last few months, based on news and market activity,
price adjusted from around 800 to around 630 today and that is the real market value...
You think Gox is going to linger for years? come on... the "sustaining"
that you are talking about is done... gox is gone, and $630 USD is what people are willing to buy and sell
a bitcoin for today.