Is the minimum amount of money required to purchase >50% hash power equal to max worth of all existing bitcoins? 20 BFL Bitforce Mini Rigs (each, $30k) will give about 30THash/Sec hash power for $600k. That's way above 60% of hash power of then total 51THash/Sec.

10.694M total Bitcoin * $18.5 current mtgox best ask rate = $197.839M

So, BFL should ship at least 6595 such miners, or price it based on, (total worth of all Bitcoin / no of miners planned to ship).

Does this mean, these miners priced so low, or currently bitcoins comparatively valued so high? Or, these two parameters just unrelated?

Please note that these miners are yet to be shipped.
OK, the question here is worthless anyway for 2 reasons.


Getting 51% hashing power over the network doesn't give you all of the Bitcoins.  All that does is allow you to spend Bitcoins, and then later roll back the blockchain and spend them again.. If you've let the blockchain commit 6 blocks to get a "real" transaction committed, then it's going to take you a while to undo that whole chain as the rest of the network continues to run away from you with the soon to be previous real blockchain.  That's going to be expensive because if one person or group thinks they can do it, then you can bet two people or groups will think they can.. All so you can buy your pizza again with your same bitcoins, and steal some petty amount of money from whomever you spent it with the first time.. Your reward isn't all the money (unless you think you can catch up 4 years of signed blocks.. dunno maybe you could), and even if it was, it wouldn't be worth it.  
If you do pull off this Bitcoin coup.. What are you really going to do? It isn't run away with 200 million USD. It's destroy the value of Bitcoin.. at least until balance is restored (in which case, you've stolen nothing). You think Mt Gox is going to let you cash out when you send them the coins from their wallet that you've taken by rewriting the blockchain? Do you think they even could? You think you'll find the market depth to cash it all out? I can tell you now.. You won't.. Even if you use all the exchanges, it won't be there.. You'd be stealing more coins than actually exist. I know I've personally destroyed 280 of them. I've heard of many others destroying more.. You'd get them back in the full rewrite of the blockchain required to steal everything, but the USD behind those doesn't exist on the exchanges.. It never did.. In theory, you could steal the sum of all the asks on all the exchanges if you could undo enough transactions to do so.. If you didn't time it right though, a lot of them are going to go away as the price plummets like it was two July's ago.. 


Satoshi's genious wasn't making it impossible to cheat the system (although it is very difficult), it was making it so that it was not to your advantage to do so. If you can hit 51% or greater, your best option is to just take 51% of the new coins.. Maybe occasionally you rewind and undo some large transactions you made with your own coins, but if you did that too much, then you've ruined yourself soon enough..