Most reliable price on coinmarketcap also you can check on coinbase and google. All source are almost same price. Different wallet showing different price due to source API. Its depend on from where they are collecting price, I mean which exchange. You will not find same price on all exchange. There will be little bit different, its depend exchange volume. But I don't think so there will be much difference.  But if you want to sell bitcoin for your own currency or USD from local wallet then its depend on them how they are following price. All local wallet will not give you same price. Some times price volatility depend on buy pressure and sell pressure. So All exchange will not same price and its not possible. So don't think too much about it. Just follow which exchange you are using.