The French forward is said to be the target of Arsene Wenger
Former Arsenal midfielder Robert Pires says the club would have to pay big money to sign Kylian Mbappe.
The France international, who's still just 18, is rated as one of the best young strikers in the world. Arsenal are rumoured to be interested, as are a number of other clubs, including Real Madrid and Manchester United.
"He's played very well with Monaco in Ligue 1 and the Champions League," he said today at the launch of Arsenal's new jersey.
"I don't know what will happen with him, but he will be very, very expensive."
Arsene Wenger is said to have cooled his interest in the French teenager, who looked to set Arsenal back north of £100m.
The veteran manager appears to have turned his focus to Lyon striker, Alexandre Lacazette.