The countdown clocks aren't costing a huge amount of money themselves. They're part of a larger program, PA/CIS, that is an outgrowth of revamping the signaling system of the IRT lines. In actuality, the clocks themselves are a prominent fringe benefit that allowed the MTA to sell this program to the politicians. Politicians don't like spending money on unseen capital projects that they can't attend a ribbon cutting ceremony for. A signaling system upgrade usually falls into the "unseen" category and thus, frequently ends up on the back burner for ages. By adding in the countdown clocks, the MTA was able to give the politicians a "sexy" publicly visible aspect of the project that they could then point to as "progress".
What this project is really about is increasing the throughput of trains through the system by eliminating the old block system. The new signaling system will, for the first time in NYCT history, allow A division dispatchers to know the exact position of any train on their lines. Before, only the towers had a rough idea, which was then communicated over intercom to the dispatchers. This should help to improve safety and increase system capacity during rush hour on the super crowded 4-5-6. As a side benefit of the computers knowing where any particular train is at any given time, the system can then calculate when the next train will arrive at any given station. At that point, it was just a matter of installing a message board to convey that info. The message boards will also give us the familiar announcements about watching the gap, saying something if you see something, etc. Along with the message boards, they're revamping the PA systems in stations, which will then be connected to dispatch, the token booths (yes, interestingly enough most station agents couldn't address the station over a PA system if they wanted to).
So, I for one, think that this is a good thing.
5th generation from Harmon (Croton-on-Hudson, NY), home of the MTA MNRR Harmon Shops.
B.S. Elec. Eng. Tech., Rochester Institute of Tech.
"I have problems sleeping at night when I can't hear the idling of several GE locomotives reverberating off the hills."