"a ten-ride ticket for NYP->POU is $0.38 per mile"
I'm only going on what you said.
MTA.info says this ride is 247.50 for a 10 trip ticket, with a trip of 85 miles that would be 247.50 for 850 miles, or 30c/mile.
From what I can see when doing a like-for-like comparison between the UK and the northeast US, the US is surprisingly pricier than the UK.
Now to be fare the Salisbury weekly season is valid for 10 journeys (or even 40), but only over 7 days, where as the Poughkeepsie one is a carnet, you can do 3 days one week, 2 days the next, and that's better, but for the Monday-to-Friday person, I'd rather be paying the Salisbury-London fare than the Poughkeepsie-NYC fare. (I'd rather be going into NYC, just without the fare)
NYP is New York Penn Station, the Amtrak station. Metro North leaves New York out of Grand Central Terminal. Sorry; the phrasing, while unambiguous to someone commuting from the Hudson Valley, was definitely confusing to most everyone else.
Metro North also sells a weekly pass for $166.75. Unlimited rides during a calendar week. The 10-ride ticket has two prices, for peak and off-peak. Peak-hour 10-ride is $247.50, as you said; off-peak is $157.25.
Very few people actually buy a weekly pass on Metro North; either you are commuting infrequently (eg, weekend commutes) in which case you want a 10-ride ticket, or you are commuting daily, in which case you want a monthly ticket. A monthly pass between Poughkeepsie and GCT is $521. If you commute 20 days per calendar month, your per-mile cost is $0.16 / mile.
Actually, since there is confusion, going back to the very beginning --
For the train route I myself am familiar with, the line between New York and Poughkeepsie, two different train systems serve the route, Amtrak (the company that does the nation-wide train service in the United States) and Metro North, a commuter-rail line associated with New York's MTA, via their Hudson Line.
I started with the Amtrak costs because the New York <-> DC train is an Amtrak train; most daily commuters will be using the Metro North, as it is cheaper.
