Actually there is no one factor that are effecting the but the and its price and also even there is nothing for the price in the altcoins , here you should be clear that the value and price of the Bitcoin or altcoin is not restricted to any laws because cryptocurrency is made to make the flow of money without any control under any law .
Here all things depending upon the demand in the market ,  I means to say that the price is mostly determine by the exchange only because people making buy and sell according to the big at the exchange , so the price will be zero $ if you will sell at 0$  , As no one is stupid so mostly the price remain at high according to demand and supply .
If any bad news will.enter in market then many people starts to make sell , so in that case demand will get down so price will get down because everyone want to sell but less no. of the people want to buy , so this is usual to get the price down .