The entrance is 10UAH (little over $1). We were there when there were tons of tourists which bugged me a little. I wanted to enjoy the castle atmosphere and wander around but there were couples taking pictures of each other, giggling and making out everywhere, not caring much about the castle. That was upsetting. But we were there long enough for those tourists to leave and then it became quieter and much nicer.
Tons of souvenirs, all of them standard, although I do recommend a lady that sells handmade dolls. she makes them herself, and you won't regret buying a doll from her. I met her at the bottom of the hill.
The downside of the place is that the castle is located on a steep, steep hill! there's taxis and if you are with elderly or someone on a wheelchair, you should really consider that option. Walking up the hill was very challenging and especially in the blazing heat that might be challenging for some people. Same goes about wheelchair access. Forget about it. Unfortunately, like with many other places Ukraine is not yet equipped for that.
Another thing is public bathrooms. you have to pay for those.
But overall experience and various exhibitions in the castle quarters were quite nice.