title: Add a Woocommerce cart fee does not persist in checkout
body: <p>I use add_fee method to charge my cart price. It works and it is OK but when I click the checkout button and I go to the checkout page or I refresh the page the new price disappear and old price is there . How can I save my price in cart?  </p>
  
  <pre><code>function woo_add_cart_fee($cart_obj) {
      global $woocommerce;
  
      $count = $_POST['qa'];
  
      $extra_shipping_cost = 0;
      //Loop through the cart to find out the extra costs
      foreach ( $woocommerce-&gt;cart-&gt;get_cart() as $cart_item_key =&gt; $values ) {
          //Get the product info
          $_product = $values['data'];
  
          //Adding together the extra costs
          $extra_shipping_cost = $extra_shipping_cost + $_product-&gt;price;
      }
  
      $extra_shipping_cost = $extra_shipping_cost * $count;
      //Lets check if we actually have a fee, then add it
          if ($extra_shipping_cost) {
              $woocommerce-&gt;cart-&gt;add_fee( __('count', 'woocommerce'),   $extra_shipping_cost );
          }
  }
  add_action( 'woocommerce_before_calculate_totals', 'woo_add_cart_fee');
  </code></pre>