You guys forgot to mention network security (look up the 51% attack) What is the cost of security and how do you even go about measuring it?
good question
Ah. It is a good question. The network does have disincentives that make a 51% attack illogical. If you have that much hash power you could attack and crash the market. It will destroy the price temporarily and your fake coins will be not be valuable enough to pay for the operation. In other words you could do it at a huge loss. Or you could use your hash power to create real coins with value and make a profit. Only an evil miner with money to lose launches a %51% attack. It would not end BTC either, it would be disruptive and hurt, but not kill. So why do it?
The only one having a true incentive to disturb the network in such a way would be a government or some entity who was trying to destroy BTC for good. In that case money wouldn't matter because they would be doing it out of some other reason.
The beauty of bitcoin as a self regulating system is that there is no incentive to destroy, since after putting all that time, effort and energy into it, you would benefit more from keeping it alive and being part of the network. Andreas Antonopulous explains it nicely in one of his speeches.
But what if it threatens you somehow? What if you are a bank and believe your business model is seriously threatened by Bitcoin? Or you are a country that feels the need to being able to control the monetary supply? You could then decide to attack Bitcoin in any way you can think of.