But in a commuter rail system like SEPTA with numerous stations that
are lightly used, there is a steep infrastructure cost in the
installation of fare vending machines at every station, and in most
places, on every platform (going from one platform to another often
requires a long walk through a tunnel or over a bridge at the
street.) Fare machines need comm lines which would have to be
installed. They would need to be visited periodically to be emptied
of cash and refilled with ticket stock and ink, and repair vandalism.

It doesn't have to be all or nothing. In San Francisco, the Muni
streetcar lines run partly in tunnels and partly on the surface, not
unlike the way they work in Philadelphia. In the tunnel, there are
ticket booths where you either pay or tap as you pass through the
turnstile. On the surface, you use the tap reader in the car or pay
the driver, who gives you a paper transfer. Retrofitting the tap
readers can't be that hard, they've put them in all of the PCC cars on
the F line. and the cable car conductors have portable readers.

Actually, if going to POP, a paper based system like the River Line
would do the job and I don't see any advantage to an electronic
ticket.

Smartcards have other advantages. For example, at this point to get
the joint PATCO-SEPTA fare, you have to stop at a PATCO machine and
buy the discounted SEPTA ticket every time you plan to make a
transfer. With smartcards, you just tap at the entrance to each and
it charges you the right amount.

To me, electronic tickets are only justified with turnstiles.

Many transit systems disagree with you.

R's,
John