His balance is just exceptional; you cannot tell which way he'll go on any play and it totally bamboozles markers. He's top percentile in the game as far as balance and dribbling go: the Messi, Hazard type class and it buys him and his teammates so much time.
What is assuring about his play is the certainty he won't lose the ball often when carrying it, which means players can run off him and ahead of the ball without worrying about the play breaking down and causing them to then be out of position on the counter. Not only that, his passing is such that he can then pick out accurate, forward passes to those runners, or use them as decoys for his own runs. He really is a quality player, and the traits he has mean he can do all the solo stuff but also instaneously switch to a team-based game in a flash. He was even working defensively last night, which is something that he isn't known for.
Sancho was the best player on the pitch last night in a tight game; if he keeps that up in the CL, his value is going to rise, even from what it is now. You have to wonder what he'll be valued at if the CL is a success and he has a strong showing at the Euros.