Harry Potter and the Wizards of Arbitrage

I suspect that the Silicon Graybeard will get a kick out of this:

So not only is the wizarding economy almost completely decoupled from the Muggle economy, no one here has ever heard of arbitrage. The larger Muggle economy had a fluctuating trading range of gold to silver, so every time the Muggle gold-to-silver ratio got more than 5% away from the weight of seventeen Sickles to one Galleon, either gold or silver should have drained from the wizarding economy until it became impossible to maintain the exchange rate. Bring in a ton of silver, change to Sickles (and pay 5%), change the Sickles for Galleons, take the gold to the Muggle world, exchange it for more silver than you started with, and repeat.

Wasn't the Muggle gold to silver ratio somewhere around fifty to one? Harry didn't think it was seventeen, anyway. And it looked like the silver coins were actually smaller than the gold coins.

Then again, Harry was standing in a bank that literally stored your money in vaults full of gold coins guarded by dragons, where you had to go in and take coins out of your vault whenever you wanted to spend money. The finer points of arbitraging away market inefficiencies might well be lost on them.

Man, this is some unusual fan fiction, that describes the world of J. K. Rowling in a, well, realistic manner:

Harry nodded, his smile widening. He sensed the work of a competent Slytherin. "And what does it really do?"

"It's a Time-Turner. Each spin of the hourglass sends you one hour back in time. So if you use it to go back two hours every day, you should always be able to get to sleep at the same time."

Harry's suspension of disbelief blew completely out the window.

You're giving me a time machine to treat my sleep disorder.


You're giving me a TIME MACHINE to treat my SLEEP DISORDER.


YOU'RE GIVING ME A TIME MACHINE IN ORDER TO TREAT MY SLEEP DISORDER.


"Ehehehehhheheh..." Harry's mouth said. He was now holding the necklace away from him as though it were a live bomb. Well, no, not as if it were a live bomb, that didn't begin to describe the severity of the situation. Harry held the necklace away from him as though it were a time machine.

This is just insanely clever.  There are 85 chapters, and I've only scratched the surface - it's fan fiction, so who knows what lurks therein.  But what I've read here is superb.

Harry Potter and the Methods of Rationality.  Well played, sir.  So very, very well played.