This is the true nature of bitcoin. The price is dynamic and the fluctuation is a normal thing.

However, the sudden huge decrease in price is due to the huge selling by the Chinese. Traders have booked their profits at $780 level and due to the huge volume of sell trades, the price went down. These dynamic pricing is the main reason why it is not accepted by the major e-retailers like amazon and all.

However, I see no reason to panic as of now. The price will bounce back soon.