Looks like my $400M estimate may have been a tad low...
"Tucker is expected to be the highest paid free agent in this class. Most analysts believe he will get somewhere between $500 million and $650 million based on the recent contracts of Vladimir Guerrero Jr. with the Blue Jays ($500 million) and Juan Soto with the Mets ($765 million). Tucker can impact a game in so many ways with his five tools: hitting, power, defense, arm strength and speed. He has made four straight All-Star teams and is putting together another strong season, batting .265/.377/.457 with 18 homers and 24 steals in 26 attempts. The Cubs would love to retain him, but the open market will determine where he’ll land and he’ll be the biggest prize in free agency."
https://www.sportingnews.com/us/mlb/chicago-cubs/news/cubs-kyle-tucker-650-million-contract-update-no-1-free-agent/4a4719de8597ed0015b970be