I just asked my wife, and she said we only paid 20k for local prices (which we are eligible for), bought onsite. Non-local price is more, not sure of the exact price. I don't recall if the price was printed on the ticket or not.

The ticket lines on site were not long, so if in doubt about pricing, buy onsite. I've seen some references to $18 for foreigners, but USD is not a legal way to charge on location within Indonesia because of a law passed a year or two ago.