Is that serious? How do you get those cheap prices? If I build up a rig with say 3 x 280x gpus that have around 3 x 710 KHash/s = 2130 KHash/s I have to pay at least:
100$ Motherboard
3x 500$ 280X GPU
25$ Ram
3 x 30$ Riser Cables
230$ 1000 Watt PSU
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Total: 1945 $
Based on the pictures, it looks like they're running Gigabyte R9 270s. They've been as low as $189.99 in the States in recent history. They can run up to 500 KH.
Riser cables are around $5 if ordered in bulk from China. (
http://www.dhgate.com/product/1x-to-16x-pci-e-extension-cable-with-powered/182319119.html#s1-4-1|4196888224).
It looks like they're running dual power supplies on each machine, probably around $90 each on sale (looks like there might be a Coolermaster V650?).
$100 Motherboard (one looks like a Gigabyte GA-Z77-D3H)
5x$190 Gigabyte R9 270 (Assuming they grabbed them on sale)
$25 RAM
5x$5 Riser Cables
2x$90 Power Supply
~$20 maybe in extras (dual power supply cable, 16x risers, USB stick)
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Total: $1300 for ~2.5 MH