What is the registration fee for?

They have tours, you can't just walk around there's different types you can choose from

I think what you're asking about is why is there a different fee for registration as opposed to the tour cost. I can't say for sure why they do it this way, but I think it's due to the fact that each tour is different once you get to the castle itself. So the registration fee covers everything involved in getting you to the castle and then the cost of the tour is based on what you want to see and hear. It may also have something to do with the fact that the Castle is a historical landmark and that's going to affect the bookkeeping.

Fees are for different tours. We took tge evening tour. It was beautiful and romantic.

If you reserve online, there's a $8 per ticket fee