Keisei Skyliner

We want to take the Keisei Skyliner from Narita Airport to Ueno Station.  I'm not a resident of Japan and looks like there is a discount if you purchase your tickets before arriving in Japan.  is that correct or can you still get the discount at the airport?   We wanted to also add on the 72 hour subway pass to the roundtrip keisei skyliner ticket.  

You can by the Keisei skyline ticket plus the 72 hour Tokyo metro ticket at the airport at the same price I think.

the details are on this website. http://www.keisei.co.jp/keisei/tetudou/skyliner/us/value_ticket/subway.php