title: Change product prices via a hook in WooCommerce 3+
body: <p>IN WooCommerce, I need to multiply all product prices by a number. So I have used the following <em>(via a plugin)</em>:</p>
  
  <pre><code>add_filter('woocommerce_get_regular_price', array( $this, 'my_custom_price'), 99);
  add_filter('woocommerce_get_price', array( $this, 'my_custom_price'), 99);
  
  function my_custom_price( $original_price ) {
    global $post, $woocommerce;
  
    //Logic for calculating the new price here
    $new_price = $original_price * 2;
  
    //Return the new price (this is the price that will be used everywhere in the store)
    return $new_price;
   }
  </code></pre>
  
  <p>But, that <strong>doesn't work for variation products.</strong> I have tried the following hooks with no luck:</p>
  
  <pre><code>add_filter('woocommerce_get_variation_regular_price', array( $this, 'my_custom_price'), 99);
  add_filter('woocommerce_get_variation_price', array( $this, 'my_custom_price'), 99);
  </code></pre>
  
  <p>The only one that works half way is this one:</p>
  
  <pre><code>add_filter('woocommerce_variation_prices_price', array( $this, 'my_custom_price'), 99);
  </code></pre>
  
  <p>But that just changed the overall price, not the selected variation price. See the image below, price is BsF. 200 and the overall price is right, 200 x 2 =  400, but the variation price when selected still shows 200:</p>
  
  <p><strong>Note: I need it to actually change, so display html hooks wont work.</strong></p>
  
  <p><img src="https://i.stack.imgur.com/4xJU2.png" alt="Variation Price"></p>
  
  <p>Is there anything I'm missing, or something wrong?</p>