Surpising Behavior

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  amountInCents: 100,
  amount: Ember.computed('amountInCents', {
    get: function(key){
    	return this.get('amountInCents') / 100;
    },
    set: function(key, value){
      this.set('amountInCents', value * 100);
      return value;
    }
  }),
  actions: {
    toggleEditMode: function() {
    	this.toggleProperty('isEditMode');
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle'
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{my-component}}
<br>
<br>

templates.components.my-component.hbs

<button {{action 'toggleEditMode'}}>Toggle edit</button>
{{#if isEditMode}}
{{input value=amount}}
{{else}}
{{amount}}
{{/if}}

twiddle.json

{
  "version": "0.4.8",
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.8/ember.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/1.13.9/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.8/ember-template-compiler.js"
  }
}