"I should have the whole amount ready by the end of the month." It would take his arbitrage trick, but certainly the Headmaster would let him do that instead of going into debt to Malfoy.
Even if he does his arbitrage trick, what benefit would he get from telling it to Malfoy in advance. Why share unnecessary information with a potential adversary? Why risk additional penalties if something unexpected happens and the arbitrage takes five weeks instead of four?
The point there was to avoid the "I can't let you do that, Harry" by making it obvious to Dumbledore (who knows Harry's current wealth) that Harry has a trick up his sleeve. Mentioning the arbitrage trick in public would be a terrible decision, which is why Harry just thinks that.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 81, which should be published later today. The previous thread passed 400 comments as of the time of this writing, so it will pass 500 comments soon after the next chapter is posted, if not before. I suggest refraining from commenting here until chapter 81 is posted; comment in the 12th thread until you read chapter 81. After chapter 81 is posted, I suggest all discussion of previous guesses be kept here, with links to comments in the previous thread.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.) When posted, chapter 81 should appear here.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight,nine, ten, eleven, twelve.
As a reminder, it’s often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: