Update price via AJAX
The answer is that "Commerce Product Bundles" (https://www.drupal.org/project/commerce_product_bundle) is never recommended since it circumvents large portions of Drupal Commerce. You should consider using line item fields or https://www.drupal.org/project/commerce_bundle if bundling is important to you.

Note: Custom line item fields also suffer from not having ajax updates. The community effort to make this a reality can be found here: https://www.drupal.org/node/1541886 and a video that describes an interesting use case for line item fields is here: https://www.youtube.com/watch?v=j9KsyvQZaAY