Have no idea how to accurately calculate this, but to get the ball rolling  

I will say it's far larger than our current marketcap:  $16,000,000,000

Taking into account, how most folks pay a fee sending to their exchange(s) and Sellers on Localbitcoins charge 5+% margin, etc

it does not take as much as any of you think...

the market cap is not based on actual fiat bank notes.

here are 2 examples
1. if we contacted every trader on the top 3 exchanges, and ask all of them to simply move their sell orders up to $2000+ and never sell below $2000. then without spending a dime th price will become $2000.

2. exchanges do not hold all 13mill coins in exchanges, you will find that exchanges normally only hold 10k-1mill coins and not all of them are actually on the sell order wall at the same time. now out of the coins that are on the sell wall. they are spread out at prices from todays value all the way up to whacky prices of many thousands of dollars (yes there are some people that have put in whacky orders and left them there longterm).
so all that matters is the number of bitcoins between todays price, and $2000. well bitstamp, btc-e, bitfinex may have anything from 100 coins to 50k each. meaning maybe 150k btc is all that is is needed to cause the price rise

in short a free collective decision can cause a price manipulation to show a new market cap of $24bill
in short buying under 50k coins on one market can cause a sheep following scenario of the other markets (panic buying)
in short buying 150k coins on all the main markets can cause the price to rise

and the most it would cost is well under $300,000,000 to make a $6bill market turn into a $20bill market

and now you will understand the term "its too volatile" because the price can be manipulated to show a market cap that does not actually have $6bill+ bank notes lingering around to hold it up.

the market cap is not a measurement of bank notes spent, it is just a average value of all coins at a current price. which can change, EASILY

Cheers lads, had to read through slowly  

You make some excellent points I didn't consider. Naive considering I trade almost everyday, but exchanges cannot/should not influence the price. The orderbook should be dependent upon clients BUY/SELL orders. By that rationale, a collective manipulation is theoretically possible.

Your approx. $300,000,000 injection estimate (well explained thanks!) does make sense and true, a lot less than I had previously envisaged.

The coins I trade each day may have past between different owners many multiple times, so I guess difficult to address original question - how much has been spent on bitcoin, thus far? Some of my coins may have been traded 12 times (12x$450) transferring more FIAT.

Thanks again for your thoughts, good brain workout for me!




re: Huobi, from what I understand, the CEO wants to facilitate a more social trading/networking environment, don't know how robust this model will be. Can understand why some exchanges chose to exercise restraint gaining formal licensing - fair point!


  

So basically, you used a lot of words to say "perception is reality", right?

That sounds right.