Find sum by property Angularjs

HTML

<script src="https://code.angularjs.org/1.4.9/angular.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/angular-filter/0.5.8/angular-filter.js"></script>
<div ng-controller="MyController">
  <ul>{{items}}
    <li ng-repeat="(key, items) in data | groupBy: 'Id'">
      id: {{key}}, price: {{items[0].price}}, Sum: {{getVolumeSum(items)}}
    </li>
  </ul>
</div>

JavaScript

var myApp = angular.module('myApp', ['angular.filter']);

myApp.controller('MyController', function($scope) {
	$scope.data = [
  	{Id:1,price:500},
    {Id:1,price:200},
    {Id:1,price:150},
    {Id:2,price:500},
    {Id:2,price:450},
    {Id:3,price:100},
      {Id:3,price:100},
        {Id:4,price:100}
  ];

	$scope.getVolumeSum = function(items) {
  	return items
    .map(function(x) { return x.price; })
    .reduce(function(a, b) { return a+b });
  };

});