add_action( 'woocommerce_before_shipping_calculator', 'add_custom_price'
     );
      function add_custom_price( $cart_object ) {
         foreach ( $cart_object->cart_contents as $key => $value ) {
         $value['data']->price = 400;
        }
     }

add_action( 'woocommerce_before_calculate_totals', 'add_custom_price', 20, 1);
function add_custom_price( $cart_obj ) {

    // This is necessary for WC 3.0+
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    // Avoiding hook repetition (when using price calculations for example)
    if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 )
        return;

    // Loop through cart items
    foreach ( $cart_obj->get_cart() as $cart_item ) {
        $cart_item['data']->set_price( 40 );
    }
 }