@Jon:

On the contrary, I think your calculations are exactly right.

Suppose you go to a loanshark and say, "The guy who was supposed to buy the wine for our party is stuck in traffic and won't get here until after midnight, but I need $2754 right now!"

The loanshark (being keenly aware of the discounts available in the retail wine business) says, "Okay, I'll loan you $2754 right now, but I'll send my boys over first thing tomorrow and you'd better have $3240 or you'll be needing some very expensive knee replacement surgery that afternoon."

What interest rate is the loanshark charging? He's charging $486 on an overnight loan of $2754. That's 17.6% per day or 6441% per year simple interest. If he can compound that return daily for a full year he would be able to buy the entire known universe before it was over. He'd probably run into some practical limitations before he reached the full 159 octilion dollars he could expect from lending out the 364th day's mere $135 octillion at 17.6% for one last day.

And, of course, those practical limitations are directly connected with the ones I referred to in my article. Stockpiling only provides these outsized returns for things you're going to buy anyway. There is no rate of return on stuff that you weren't going to use.