And there is leverage, so you can invest 100 $, but get profits or loses like you invested 10000 $. So if theres 100x leverage, and 1% profit to make on currencies each day, you can double your money every day.

So to turn 100 galeons to 100000 galeons Harry would need 10 transactions with 1% profit each.

http://www.investopedia.com/ask/answers/06/forexleverage.asp#axzz1qS7tVBFp

So everybody except Harry are holding idiot balls?

Great point. If Harry is Voldemort, Voldemort will keep Harry money because Lucius have them. If Harry is not Voldemort, Voldemort will earn Harry money, because Lucius have them now.

Win-win once again. Lucius is a competent player, and Harry is underestimating him.

So if Hermione is vassal of Harry, and Harry is temporary vassal of Lucius, then is Hermione vassal of Lucius?

Or do the muggle medieval rule "the vassal of my vassal is not my vassal" works in magical Brittain also?

Oh, right.

It's funny how we(I) take some things for granted.

Yeah, phrasing it right wouldn't be trivial, but much easier than making wishes for UFAI, because Veritaserum is the equivalent of perfect box for AI, and Draco is human, so most of the definitions and assumptions he shares with the judges.

So maybe: "Tell me the things, you think I would want to know about, according to the best model of me you can construct."

With heavily leveraged trading on forex ( http://en.wikipedia.org/wiki/Foreign_exchange_market ) , he can make 100 galleons into 100 000 galleons in one hour (with leverage of 0.2% you earn profits from trading of X, but you only need to really have 0.002 of X). And you can do this over internet, by a few back and forth trades that lasts for a few minutes.

We don't have a way to be sure our universe runs on casuality. It's just generalization from our experiences. The same could be true for Dumbledore and his universe.

If regular courts had veritaserum, I imagine the first question they'd ask would be "What are the things you don't want to tell us?".

Arbitrage trick is overengineering. Just trade on forex and use time turner to go back and choose the deal.

With 40 000 galleons even going back a few minutes could suffice.