Thank for the post and question. It's going to depend on where you want to taste En Primeur in Bordeaux. There are some estates that require appointments, especially The First Growths and perhaps 20-30 more of the top name in Bordeaux. Some Bordeaux chateau limit the number of people they allow to taste. Others are open.
If you ask me about specific chateau names, if I know, I am happy to share the info.
As for your other question, there are no fees for the tastings of En Primeur Bordeaux wine. At least I've never heard of any being charged.