Context is referring to extremely good actors: "What happens when A, B and C are on set is magic. In all honesty it doesn't take a whole lot to get them there"
Taking into account A, B and C are screen stars, that seems to mean it is not easy getting them together in a movie. So, what may mean the last sentence ( In all honesty it doesn't take a whole lot to get them there) that appears to say it was not hard to get them on set? Or maybe the sentence means "They had a good time, built friendship and all was easy at work in the set despite stardom?