Sorry missed that. Reading comprehension fail. Should then be 1 in 120 then with a $600 valuation per coin. Comment about "good chance" being misleading still applies.
I don't know nuthin about pricing risk, which is why I tell all of my relatives I have absolutely no idea whether or not they should buy Bitcoins.But: it seems to me you're assuming that the entire $5 current price of Bitcoin is pure speculation, and ignoring that they ARE functioning as money in some fledgling markets. And don't you have to factor in time value of money into the calculation? I'll pay a lot more for bitcoin today if I think there's a 30% chance it will be worth $600 in a year than if I think there is a 30% chance in 100 years.
You're also assuming that the velocity of bitcoin will be approximately equal to the velocity of traditional currencies. I could image it being much higher (less friction in transactions, so more transactions) or much lower (maybe bitcoin will be used mostly as a long-term store of value, with infrequent transactions; what is the velocity of an gram of gold compared to dollars?).