Basic selectors idea.

README.md

The state shape would be something like:

{
    products: [
        {
            price: 7500,
            name: "Some product",
            //other details
        },
        {
            //More products
        },
        //...
    ],
    //other state
}

TotalPriceContainer.jsx

let React = require('react');
let { connect } = require('react-redux');
let totalPriceSelector = require('./totalPriceSelector');

let TotalPriceContainer = React.createClass({
    render: function() {
        return (
            <div>
                Total price: {this.props.totalPrice}
            </div>
        );
    }
});

let selector = function(state) {
  return {
    //state, //You could include the raw state if you want, as well.
    totalPrice: totalPriceSelector(state),
  }
}

module.exports = connect(selector)(TotalPriceContainer);

totalPriceSelector.js

let selector = function(state) {
    let total = state.products.reduce((total, aProduct) => {
        return total + aProduct.price;
    }, 0);
}

module.exports = selector;