It is indeed very expensive, I bought it for around £300 in November and I've seen it up to £400 recently.
But it's the best power supply money can buy, it overclocks to 1600W + you can set it to power up your miners with no need for shorting ATX pins.
I would say most miners will be better off with 2 cheaper power supplies instead of this one (it'll cost much less) but in my case once I'm done with mining I can always use it to build a PC with it.