But still, they are cheaper than a mining rig composed of graphics cards.
They are not cheaper, at least not if you count shipping and import fees and you live in the US. I only say US cause that is where I did the calculations.
You can easily find cards that for $260-$275 today.
6 x $275 = $1650 + $400 for other parts
That is about $100 less cost of the asic with PSU + shipping + import fees.
Benefits of the gpus... more algos, more fun
Benefits of the asic... Uses slightly less electricity, less hassle
I'm not saying one is better than the other, however if GPUs drop by 10-20% next month like everyone is saying... GPUs will be the clear choice.