At first I thought that the $50 charge was a change from last year. But, in looking back, we went in May last year and that's when they begin manning the information building for the season. I can give the tour for free.

Their tour is just inside the furnace stack, a side room that is a mini museum of tools, and the "iron pig" room. You can peek in the windows to see what's inside for the most part. The only thing missed would be looking up & photographing the furnace stack which several of us have done.
I'll be there at 9AM hanging out either in the parking lot off of Franklin Street or in the bluebell field (if they are still there).