But they get $8000 or close to that because they sell all at once, and not only that - they probably buy back some coins when price is drop to $6200 on Bitstamp. This is win-win situation for big players who can move market in direction they want anytime.

Imagine a possible scenario, few months ago you buy 5000 BTC at the price of $3000, which is investment worth $15 million. Today you sell those coins at price close to $8000 and get $40 million, profit is $25 million. In case you manage to buy at lowest price ($6200) you can get your 5000 BTC for $31 million and enjoy in $9 million of profit, you have bitcoin and cash - I would not call them morons