Are angular $broadcast and $on expensive?

Question

I've been told that using angular events can be expensive (I've been unable to verify this)

Any calls to $broadcast and $on should be 'wrapped' with a factory or service to inject into their corresponding components to preserve performance?

Again I'd rather use $on and listen directly to the events being fired rather than creating a factory that in essence is just going to register functions to call when it receives the event - lets call this a dispatcher.

Please note that it's not just one component (directives) listening to 'some-event' there will be a variety of components listening to this event.

Example dispatcher:

angular.module('app').factory('dispatcher', ['$rootScope', function ($rootScope) {

    var registeredFns = [ ];

    $rootScope.$on('some-event', function (evt, msg) { 
        _.each(registeredFns, function (fn) {
            fn.apply(null, msg);
        });
    });

    return {
        onSomeEvent: function (fn) {
            registeredFns.push(fn);
        }
    };
});

And inject it where I need it - maybe a directive, maybe a controller where ever it doesn't matter.