public function subItemsTotal($format = true, $taxedItemsOnly = false, $withTax = false)
    {
        $total = 0;

        foreach ($this->subItems as $subItem) {
            $total += $subItem->price(false, $taxedItemsOnly) * ($subItem->qty ?: 1);
        }

        if ($withTax) {
            $total += $this->tax * $total;
        }

        return LaraCart::formatMoney($total, $this->locale, $this->internationalFormat, $format);
    }