I looked up the Exton, PA, train recommended by Walter. It looks like a good option (no more than an hour's travel from Phila., and probably still less than $10 each way, though I can't vouch for that) -- but I found all sorts of delay warnings from Amtrak due to another station being built nearby.
However, the SEPTA light rail schedule to and from that station lists frequent trains:
https://www.septa.org/schedules/rail/pdf/tho.pdf