On Saturdays, your customers can receive two-day packages from FedEx. Cost? An extra ten dollars. On Saturdays, your customers can receive two to three-day priority mail packages from the U.S. Postal Service. Cost? Three dollars, and there's no extra charge. On Saturdays, your customers cannot receive two-day packages from UPS. Sorry. So, what's your priority? Priority mail from the U.S. Postal Service.