My guess is some, if not all of those locations you mentioned were considered at one point by Apple, and are probably under consideration right now by other companies such as Google, Amazon, Facebook, etc.
These companies undoubtedly have a long checklist of items that they need to review:
- Where is there a good amount of land for sale suitable for development of a server farm? What is the price of the land? Potential for expansion in the future?
- Is it zoned for commercial development? If not, how difficult would it be to change the status with the local zoning committee?
- What are the property taxes on said parcel?
- What would the cost of developing the property be? How long would it take?
- What accessibility does it have to an airport (for equipment deliveries), large city (to attract qualified candidates)?
- What is the availability of renewable energy sources and the cost?
- Is the local government willing to barter concerning taxes and fees? If so, how much so?
- and so on...
No site will be optimal for everything, there would have to be some concessions made, just like any real estate transaction.
Servers are servers, routers are routers, and basically cost the same wherever they are located. The land purchase is a one time expense; however, the biggest variable ongoing expenses for a large server facility that that would be utilities and taxes.
In the end, Apple probably wittled down their potential sites to less than a half dozen and proceeded to negotiate with the local authorities/power companies on the latter two.
Somewhere, Prineville came up on top. We'll probably never know why since Apple would not discuss the details of the negotiations with other sites. By law, the public has the right to know of any special deals the local government cuts.
However if Apple struck a deal with a private power company concerning rates, that would be private matter.
You can't base Apple's projected power costs looking at a retail power bill and consumer power rates. Corporations get different rates.
Do you think Amazon.com plays UPS the same amount to ship a 1-pound package as you would pay if you walked into a UPS Store?