I know I don't have much money, but I have been waiting for months to get a copy of this and it's only £10. If you get it now you get the digital download copy for £10 and you get sent a free physical copy of the game too (should be £15). So it's a reasonable amount when you consider it is a modern interpretation of the game from the 1983 film WarGames and thus allowing you to recreate an authentic 80's atmosphere in your computer's vicinity if you so choose.
Defcon will be available to download and play to everybody who pre-ordered September the 29th at 6:00pm (GMT).
Additional: Defcon MIGHT be cheaper on STEAM, but I don't know because I am yet again having that login problem (started just now) that will require Valve to do something on their servers for me to be able to login again. Here is a pre-order link to their pre-order if you are interested. It says $9.95 on that page, but I don't know if that is before they add UK VAT if indeed they add UK VAT. So I don't know if it indeed cheaper from STEAM or Introversion. Still you don't get a boxed copy and I hate giving money to Valve.
Update: Valve