Never thought I'd see this in print, but the MTA let NY Times publish a distribution of Metrocard usage for monthly passes (see below).
While the caption of image points out that "some riders use the $81 passes for 40 or fewer rides," it fails to point out that anyone making 46* or fewer trips is losing money on their pass. The calculus of "losing" or "making" money on a monthly pass is of course fraught with nuance (e.g. how much is it worth to me to not have to think about paying on each trip? are any of these passes subsidized?) but the article doesn't touch on it at all.
It's no secret that I love NYC Transit and transit in general, but that doesn't mean people should be buying passes when it's far from beneficial. Don't even ask about the London case...
* 46 trips is the breakeven point when the monthly pass cost $81 and individual trips cost $1.74 (after the bonus)