On the 20th of every month, I get a transitchek metrocard with my paycheck at work, and the cost of the card comes out of that paycheck, tax-free. In the past, when the cost was "only" $89 each, I have always ordered 30-day unlimited metrocards, but was often curious whether I was actually realizing that value every month. Now that the same metrocard costs $104 each month, I figured it could not possibly be worth it, and I opted instead for pay-per-ride. With transitchek, this meant that on January 20 of this year, for $96, I received two $48 pay-per-ride metrocards (worth $51.36 with bonus) that were supposed to last me through February 20.
It is now lunchtime on February 9, and I have exactly $2.25 left in subway fare. That's one ride to get me home from work tonight, and then ten days of extra costs I could have avoided. Even assuming I do nothing but go to and from work from now through the 18th (the 20th falls on a weekend), which is usually not the case, I need 14 more rides to get me there, after I use my last $2.25 tonight. Those 14 rides will cost me an extra $31.50, bringing the total cost of my subway use this month to $127, when I could have paid $104. I could also purchase a 7 day unlimited card to get me through the next week, for only $30, but that would leave me again needing to purchase further rides for getting to and from work on February 17 and 18. It seems that my trial really was more of an error.
Why do I say this "may" apply to you? The links above show that the 30-day unlimited metrocard at $104 is only valuable if you use at least 50 rides per month. While you may not be able to precisely calculate exactly how often you are riding mass transit each month, consider that if you commute to and from work everyday, sometimes use mass transit to go out after work and also sometimes use mass transit on the weekends, you are probably riding more than 50 times. I personally keep a very active social calendar and know that, this Thursday I will need to take the subway to work, then to a bar for a friend's happy hour, then to another bar for a date, and finally home. That's four rides in one day. On Saturday I am attending a birthday party in Brooklyn (I live in Manhattan) and on Sunday I am getting a haircut and then seeing a play, and although I may be able to walk to the haircut and the play from my apartment, depending on the weather, I may opt for a subway or bus. That's two to five weekend rides. On Monday I am going to work, and then taking the subway to a Valentine's Day-rejection-themed comedy show, and then home. That's three rides... You get the picture.
UPDATE: Commenter Tami S. notes that you may be able to get a refund for unused $89 unlimited metrocards, as the activation time for those cards expired yesterday, February 8. I did some research and here is what I found: During the 2009 fare hike, commuters were instructed to go to any subway station and "ask a station attendant for a postage-paid envelope," to mail old metrocards in for a pro-rated refund. I called MTA's Customer Service and confirmed that if you mail your unused or partially used metrocard(s) into Metrocard Customer Service, MTA, 2 Broadway, New York, New York, 10004, and include your full name and address, you will in fact get a pro-rated refund.