So far in my knowladge that bitcoin prices are determined by various rumours that happen. If more and more the negative rumours about bitcoin then the price will have a decrease. Otherwise if many positive rumours to bitcoin then the price will rise.

Well, which happening now is, many more the negative rumours that fall on bitcoin, like Microsoft that no longer use bitcoin as their payment tool. And CEO JP Morgan's assertion that cryptocurrency will be regulated by the government.

So, that's exactly why the bitcoin and altcoin prices are down this week. Back on your qustion, my answer is bitcoin could have dropped to $400 if negative rumours arrive against bitcoin. And otherwise bitcoin prices will rise if positive rumours arrive at bitcoin.