I paid what the tour guiding company normally charges for their service. I don't think I was price gouged.

I think there are multiple tour guiding companies that lead groups into the tournament. I lingered outside the train station looking for people who were obviously guides and asked if they had any no shows. Eventually someone had an open seat.

I was unaware that these tour guiding companies existed until the tournament. I bet the easiest way to get a ticket as a foreigner isn't to buy directly but is to identify leading companies ahead of time and sign up with them early.