Ex designer of military kit
You go down to your local PC dealer of choice and get a top of the range PC - £2,000 to £3,000. Then you molly-coddle it in a nice warm office.
Now take the milaero version:
To start with, no fans. Then add that it must work in a Siberian winter and a Saudi summer. (-40 deg C to +85 deg C)
Add to that, it will be working in a tank, fighter jet or helicopter - shock, Gforce and shaking.
It might also be subjected to condensation as the vehicle warms up, or salty water if it is in a small jet boat.
And it must have the latest processor, graphics, etc. that you have in your desktop PC.
I think that adding a zero to the price is actually quite reasonable!