As noted here, it seems much better to get a CharlieCard rather than a CharlieTicket. Unfortunately, I didn't know this and bought a stored value CharlieTicket. Is there any way I can transfer the amount in my CharlieTicket into a CharlieCard instead, so I don't pay the higher ticket prices? Will the fare machines let me do this?
As usually, the MBTA is quite obtuse about this. Apparently this did work at some time (http://charlieonthembta.blogspot.com/2006/12/now-can-you-transfer-funds-from.html) but there is no current information whether this is still the case or not.
They are pretty clear that you can't redeem the remaining value of a Charlie Card for cash. It's a pretty devious system actually: the Charlie Ticket subway fare is $2.65 and the smallest default value at the vending machine is $5.00 (although you can select "other amount"). There are probably quite a few Charlie Tickets $2.35 remaining value been thrown away.
Your best shot is to go to the Charlie Card store in Downtown Crossing and ask.