That cost is the infrastructure cost, amortized over a long time, not counting R&D, maintenance, marketing, ticketing, and various personnel costs, assuming it's near capacity.
Also consider this is bus-tier people moving, not even train. You just have small individual units moving along one track. With even passenger rail, you have to have set departure times measured in at least 10 minute blocks, something like this could have a departing train every 5 minutes and you could go through a turnstable the same way you get on a subway.
Translation, it's going to cost more than $20.