Sometime people wonder how the Bitcoin price is calculated. It works no different than it would with other item. Let’s first look at how the prices of most things are calculated. Let’s use apples, just as an example. 

One would price an apple based on two things: how much the seller is trying to sell it for, and how much buyer is trying to buy it for. So if Paul wants to sell an apple for $1.50 and John is prepared to pay $1.00, THE SALE WILL NOT BE DONE. However, if they agree on a price, then the transaction will happen. 

Bitcoin or steem or any other currency for that matter, are different from apples or oranges in that they are also determined on size and quality.  This means that Bitcoin or steem have an advantage as it has no problem size and quality.  Leaving them solely dependent on supply and demand.

All country currencies work exactly the same. However, just as a countries currency will be affected by news and events, so too does all crypto currencies. This is closely related to supply and demand. Say if a country is going through so kind of difficulty, less people would like to visit or even for that matter hold that countries currency. So the demand will be less and this currency will drop.
Although, this is a simple example on how it really works. Much time the big Guys would manipulate the currencies for a profit. This too has a great impact on currencies. Let’s take the apple example again. If some big shot wants to make some money out of apples he would buy all the apples in the market and sell it tomorrow at a higher price. This was the price of apples will go up. Now, how do they drop the price? All they do is stop buying the apples and after a time the price of apple will drop. Why would they do this, Simple when the price goes down the buy it all again and because only they have apples they can dictate the price. 
I hope you can understand ,this is the basic rule of any business.