Who says they didn't perform the kind of cost/benefit analysis you mention and estimated that it wasn't worth the effort? And if that was their estimation, despite our (NH denizens) collective annoyance, maybe they were right. Maybe providing free access made prospective paying customers less likely to pay for firehose access, or a slew of not-for-profit organisations requesting free firehose access citing emojitracker as a precedent. There's a myriad of hypotheticals and whomever made this decision is not necessarily irrational... it just depends on what constitutes their utility function.

I was saying that maybe it would have been a good idea for them to publish that analysis publicly, or just to emojitracker (where they would presumably publish it for Twitter).

I don't see that as Twitter's obligation. When someone does you a favor, or makes an exception for you, it's nice if they give you a reason when they end it, but it's not their responsibility.

No, it's not their responsibility. I'm just saying that PR-wise it could have been a good move to just say, "Hey, it's costing us $X/month to give you an exception for this access. Sorry, but we can't justify that cost going forward." Are you saying that it would have been a bad move for them to say that?