OP needs to redo his math.
The long, uncertain wait is the problem. BFL anyone?
Why do I need to redo my math? You can read, right? The price is listed in british pounds. In USD it is about 8900. I can build pretty close to that 25MH for that today. Maybe spend a little more, but I'm not talking 32 $500 cards, I'm talking 40-50 ~ $200 cards. A difference of a few K here and there isn't much, especially betting on completely new, untested hardware from a new, untested company. If they start shipping and reviews are good, I may buy some, of course by then all the rigs I'm building now will have spawned many more like them from coin profit, and I likely won't need them. I suppose I'd consider selling off all the old hardware and replacing it with new for the power savings, but that can wait until products ship.
WTF LOL.
'm talking 40-50 ~ $200 cards
That's $8000 to $10000 in just cards alone.
Add on (PSU, MOBO, RAM, etc) x 8-10.
Then add on the cost of power at the wall and the cost of your time building and then maintaining all these rigs.
25MH for ~$9000 is an amazing deal.
The problem is the wait time and uncertainty of delivery. You don't know if something better/less expensive will come out before your product arrives.