If the price was $30 per year, I bet you could attract at least 400,000 casual subscribers (in an area of 24M people) and earn the same $12M per year. The more casual users would put less strain on the system too.
I wonder if the report you linked to is somehow broken ("There were 18 active Citi Bike stations at the end of March.") but 2 trips per bike per day sounds comparably low - I guess an annual report would be more useful.
> everyone wants to go to Grand Central in the morning and leave from there in the evening.
Sounds problematic (and weird) to me, like they have attracted only a specific type of potential users.