The bitcoin price is defined by exchanges. Even if they buy outside exchanges, they will need to go for them to sell and do the manipulation stuff.
How will they sell bitcoins off exchange?
I agree with the Op, the hedge funds or Wallstreet can't buy big on the open exchanges without dramatically increasing the price.
They would buy OTC (Over the Counter).
Estimates for the FBI purchase was at least $666 considering Second Market's $20 million bid didn't win a single block of BTC. Long term, this will be a bargain, IMHO.