Change price

    add_filter( 'woocommerce_before_calculate_totals', 'woo_custom_addons_plugin_custom_cart_items_prices', 10, 1 );
    function woo_custom_addons_plugin_custom_cart_items_prices( $cart_object ) {
        global $prices,$add_ons;
        if ( is_admin() && ! defined( 'DOING_AJAX' ) )
            return;

        foreach ( $cart_object->get_cart() as $cart_item ) {

            // get the product id (or the variation id)
            $id = $cart_item['data']->get_id();

            // GET THE NEW PRICE (code to be replace by yours)
            $explode = explode(" - ",$cart_item['data']->get_name());
            if(isset($explode[1])){
                $add_on_id = $add_ons->getByName($explode[1]);
                if($add_on_id !== 0 && $prices->getPricePerQuantity($add_on_id,$cart_item['quantity']) !== false){
                    $new_price = $prices->getPricePerQuantity($add_on_id,$cart_item['quantity']); // <== Add your code HERE

                    // Updated cart item price
                    $cart_item['data']->set_price( $new_price );
                }
            }
        }
    }