You'll need to buy some bitcoin first through an exchange, but if you go through Bitmain and pay with bitcoin, it comes out to about $400 per unit, but you have to buy at least 2 per order.

You'll pay up quite a bit through ebay or amazon, but you do get the security of being able to return it pretty easily if there's problems. Personally I don't think it's worth paying an extra $125 or more just for being better protected. Odds are low you'll have a DOA item.