Calculating a hash takes <1s, due to a special condition it is a bit more complicated with Bitcoins. They way they do it today is Brute Force. ASICs are perfect for this.
Expensive in developing, very cheap in producing. But you cannot do anything else with them. Once they do not use Brute Force anymore, they are dead and GPUs are much faster,
because general purpose. Got it ?
Conan
even 10 years down the line, your gpu is not going to hash as much as an usb powered ASIC.
bitcoin ASICs are useless for anything other than hashing, but GPUs are now useless with bitcoin mining. world will never ever mine with GPUs again..