They are bringing in $400 per trip. It will only take 2.5 million trips to break even. (Not counting running costs. electricity, taxes, employees, etc).
Or, looking at it another way, if the system can handle 2,000 passengers in each direction, we have 4,000 passengers each paying $25 or $100,000 of income per hour at capacity. So, 10,000 capacity hours would pay for the system (excluding maintenance and wear and tear). Assuming six capacity hours per day it would take 4.5 years to get the initial $1 billion in revenue, with the other 18 hours per day providing income for operating, maintenance and ROI.
I'd think that, if it's doable at even twice the cost, it could work. But whether it can be done for even a couple of billion is anyone's guess.