You have to know that there will always be either small or big differences on the price of any exchanges because exchanges have their own trading volumes, so there's is really no exact price for Bitcoin, so you should only rely on the exchanges you are using to exchange your Bitcoin to fiat currency. About websites that shows live prices of cryptocurrencies (like what you stated above), there are also difference on the price because some might collecting data on some exchanges and some might not, so there will always be a difference on their live crypto prices because they all don't have the same data sources.