#3 Real Madrid

The allure of Real Madrid goes without saying, but there has been a slight dip in their popularity since the departure of Cristiano Ronaldo. They've also struggled in recent months, playing poorly under Santiago Solari, resulting in the board having to recall Zidane to make amends.
Sancho would certainly fit Madrid's style of play, and therefore would get decent game time, but it's unlikely to be as much as he's currently getting with Borussia Dortmund. As a player of his calibre needs to play as often as possible to consistently develop, he would have to consider this choice carefully.
In regards to his hefty price tag, Madrid are a very rich club, and would have no qualms about paying out huge sums of money to get their target, especially if they had to compete with others for his signature, that would likely just spur them on.