Hmm I'm pretty sure the GPU cost can be lower than the CPU cost (not power/energy, just GPU vs CPU cost)
To buy the first GPU miner costs PC+CPU+GPU
To buy the first CPU miner costs PC+CPU
Firstly, however, the CPU required by the GPU miner is cheaper than that required for CPU mining.
The GPU miner's CPU hardly does any work (if you use Linux and the best ATI driver) e.g. in my case it clocks down to 1200Mhz and only use 4% of a single CPU core when mining.
The CPU miner's CPU needs to be all about performance to get more hashes so will clearly cost more the the GPU miner's CPU thus making the overall cost difference less.
Next, if you wish to increase your hashing power:
For CPU you need to buy another whole PC to add directly to your current hash value.
For GPU you can usually just add another GPU card if you bought an appropriate motherboard with more than one PCI-e slot.
To buy the first GPU miner costs PC+CPU+GPU
To buy the first CPU miner costs PC+CPU
Firstly, however, the CPU required by the GPU miner is cheaper than that required for CPU mining.
The GPU miner's CPU hardly does any work (if you use Linux and the best ATI driver) e.g. in my case it clocks down to 1200Mhz and only use 4% of a single CPU core when mining.
The CPU miner's CPU needs to be all about performance to get more hashes so will clearly cost more the the GPU miner's CPU thus making the overall cost difference less.
Next, if you wish to increase your hashing power:
For CPU you need to buy another whole PC to add directly to your current hash value.
For GPU you can usually just add another GPU card if you bought an appropriate motherboard with more than one PCI-e slot.
True but currently those GPU can yield far more mining bitcoins. No chain exists in a vacuum but you are right if somehow bitcoin died and tenebrix reigned supreme you would see GPU mining. It wouldn't have the multiple that it does on bitcoin but it would be more profitable. Eventually the cache on GPU will improve and GPU will slowly creep further ahead. Likely the best GPU aren't the top of the line ones (with top of the line price). As the scrypt algorithm limits how parallel a GPU can work effectively we may find that lower end (more narrow) GPU offer higher hashrate per $.
Still as long as bitcoin is profitable there is no real reason to look at using GPU where they are only 1/50th as effective.
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