A private transaction of BTC wouldn't effect the market value of BTC. It is correct to say 1M BTC = 565M USD; the market price of BTC/USD is only effected when the BTC is sold on an exchange.
Re:Equation Group Cyber Weapons Auction
by EthanHeilman on Monday August 15, 2016 @05:30PM
(#12293626)
Almost no single entity has that much BTC (as of 2016 only ~15 million Bitcoins exist), to acquire it someone would have to aggregate the Bitcoins from many other entities by via buys on a Bitcoin exchange. This would cause a massive spike in the price of Bitcoin.
Interesting to note: there has been no new Bitcoin block for the last 1 hour 23 minutes. This happens from time to time, but it is a little suspicious.
The block chain makes it worse because everyone can see the progress of the buyer and there's no market maker with anywhere near this level of liquidity.