If miners are egoistic and can mine other coins with the same hardware an attack would be much cheaper.

You haven't to buy the mining power you need for the attack you can just lease it. Costs for leasing are just a little bit more than miners can earn with their hardware in the time of the attack. So today leasing costs for one hour of bitcoin mining power is when you trust the calculations of digiconomist.net about 1 million $.

During the attack you also earn for mining a little bit less than the leasing costs. So large costs only come to you, I've the currency goes down during you attack.

In worst case scenario - currency goes down directly - you have thrown away the leasing costs of 1 million $ per hour, in best case scenario - nobody notices your attack during you do it - you have the win of double spending and mining during the attack minus leasing costs.

If the value of the double spended transaction is great enough there's a positive profit expected! You can only prevent this if you don't trust large transactions. But this makes the currency maybe inefficient as you see in the discussion here.

If miners are egoistic and can mine other coins with the same hardware an attack would be much cheaper.

You haven't to buy the mining power you need for the attack you can just lease it. Costs for leasing are just a little bit more than miners can earn with their hardware in the time of the attack. So today leasing costs for one hour of bitcoin mining power is when you trust the calculations of digiconomist.net about 1 million $.

During the attack you also earn for mining a little bit less than the leasing costs. So large costs only come to you, I've the currency goes down during you attack.

In worst case scenario - currency goes down directly - you have thrown away the leasing costs of 1 million $ per hour, in best case scenario - nobody notices your attack during you do it - you have the win of double spending and mining during the attack minus leasing costs.

If the value of the double spended transaction is great enough there's a positive profit expected! You can only prevent this if you don't trust large transactions. But this makes the currency maybe inefficient as you see in the discussion here.

If miners are egoistic and can mine other coins with the same hardware an attack would be much cheaper.

You haven't to buy the mining power you need for the attack you can just lease it. Costs for leasing are just a little bit more than miners can earn with their hardware in the time of the attack. So today leasing costs for one hour of bitcoin mining power is when you trust the calculations of digiconomist.net about 1 million $.

During the attack you also earn for mining a little bit less than the leasing costs. So costs only come to you, I've the currency goes down during you attack.

In worst case scenario - currency goes down directly - you have thrown away the leasing costs of 1 million $ per hour, in best case scenario - nobody notices your attack during you do it - you have the win of double spending and mining during the attack minus leasing costs.

If the value of the double spended transaction is great enough there's a positive profit expected! You can only prevent this by not trust in large transactions. But this makes the currency maybe inefficient as you see in the discussion here.

If miners are egoistic and can mine other coins with the same hardware an attack would be much cheaper.

You haven't to buy the mining power you need for the attack you can just lease it. Costs for leasing are just a little bit more than miners can earn with their hardware in the time of the attack. So today leasing costs for one hour of bitcoin mining power is when you trust the calculations of digiconomist.net about 1 million $.

During the attack you also earn for mining a little bit less than the leasing costs. So large costs only come to you, I've the currency goes down during you attack.

In worst case scenario - currency goes down directly - you have thrown away the leasing costs of 1 million $ per hour, in best case scenario - nobody notices your attack during you do it - you have the win of double spending and mining during the attack minus leasing costs.

If the value of the double spended transaction is great enough there's a positive profit expected! You can only prevent this if you don't trust large transactions. But this makes the currency maybe inefficient as you see in the discussion here.