What is the most expensive club in football?

Could you please elaborate on what makes a football club expensive? Is it the player salaries, the stadium facilities, or perhaps the overall brand value? In terms of the question "What is the most expensive club in football?", how would one determine the costliest club, and what criteria are typically considered? Additionally, could you name a few of the most expensive clubs in football at the moment, and provide a brief explanation for why they are considered so?