[glogla]

$250 is too low. But the whole setup with MBA with 512 GB SSD, 8 GB RAM and i7 CPU, the GPU and then the $250 in parts is not only enough money for powerful desktop computer, it is enough money for cheaper MBA variant and then powerful desktop computer.

[baddox]

But then you don't have a Macbook Air for when you want a great portable OS X machine with excellent battery life.

[glogla]

You would have Macbook Air, just not one with 512 GB SDD.

Of course, from the MBA with 512 GB SSD we can assume the OP has unlimited amount of money :)