I do this twice a week.
The fee to get to the Air Train is $5, and its an airport fee. You are stuck on the platform unless you pay it.
I buy a 10 trip ticket between NY Penn and NJ Penn for $2.50 per trip. When the conductor comes by again after NJ Penn I tell him/her I am going to EWR ($1.60 extra). I then pay the $5 air train fee at EWR (or you will not be able to get through the gate) for a total of $9.10.
At the EWR Air Train station hit code 099 to buy your $5 exit ticket, this code works for both exit and entrance at the Air Train station (I buy an extra one when I leave EWR so that I have it when I return to EWR so I do not have to spend the time buying a ticket at the Air Train kiosk which may result in missing the next NYC train).
Even if you do not do this as often as I do, the above will still work with a single NY Penn to NJ Penn $2.50 ticket, as I receive no discount for my 10 trip purchase.
With the $2.35 you save one way, you can buy me a beer some time :P
[This message has been edited by Joey (edited 04-03-2002).]