title: Updating the price on changing the size
body: <p>I want to update the price displayed in span as soon as the <code>product.selected_size</code> is changed. In this case product is a computed property of my component.</p>
  
  <pre><code>&lt;div class="prices-wrapper"&gt;
  &lt;span class="price-normal"&gt;&amp;euro; {{ product.prices[product.selected_size] }}&lt;/span&gt;
  &lt;/div&gt;
  </code></pre>