I think that the increase in boarding speed of charliecard vs. stored value charlieticket is not significant enough to warrant an over 30% price difference (green line $1.70 + 0.55 surcharge), especially considering that paying cash at the farebox which takes much longer than swiping the ticket is exactly the same price. The cash fare surcharge is at least arguable, for example the added time to process the fare, and cost of dealing with the money in the fareboxes (sorting, counting, etc) that does in the end cost the T a fair bit. The charlieticket surcharge (particularly when boarding the red, blue, and orange lines) is on the other hand ridiculous. Even more ridiculous is the free bus-subway transfer using the card, but double-payment using the stored-value ticket.
The real aim here is twofold: first, they are able to make the single-ride fare increase seem lower than it really is by separating the fare and surcharge during the discussion. Second, they have not stated how much a charliecard will cost. Taking Chicago's example, if would be $5 following some introductory free period. Replacement cost for a lost card is also $5. Occasional riders are faced with a dilemma: go out of their way to buy a charliecard (they will not be available at machines, you will have to go to a designated sales point) knowing that it will require several rides to break even and a lost card will require another investment, or pay the extra fare for a ticket. Most will choose the latter, and the T is counting on it. On the other hand, a reduction of single-fare rides will also be a good argument in the future for cutting service in off-peak hours.