They don't want to sell Harry Kane to their rivals. I don't think money is the problem.
I understand why Tottenham are reluctant to sell Harry Kane to another English club.They know very well that he is a good player and selling to another english club will only mean that they are empowering their rivals. Chelsea do not think this way, that is why they have made the mistake of selling Kovacic to Manchester City. Kovacic will be brought back to his best by Pep, and he will become a very good player for Manchester City that can pair with Rodri in their midfield. Chelsea made a mistake.
Tottenham are just being unreasonable. A team like Manchester United is not a rival to Tottenham. There's nothing wrong with selling their player to United. If every team decides not to sell their player to other teams in the league how will the league look? Tottenham are ciy rivals with Arsenal so it can be understandable if they don't want to sell their player to them. Manchester United and Liverpool are also rivals so they will most likely not exchange players.
Whether they sell Kane to a rival or not, it doesn't mean anything.
Chelsea did not make any mistake. They have gotten the players they want. Man City would have still gotten another player in place of Kovacic even if Chelsea did not sell Kovacic to them. You don't expect the teams in the league to not do business with each other.
Totthenham are aware of the risk involved in selling their best striker and their best player to a rival,they know quite well that he will still be the man to score against them when they meet in the premier league.you don't just have to blame them because if you were the coach you will do thesame.It is not a thing of joy that the player you sold out is thesame player that causes you headache anytime you guys meet.If Totthenham is to sell their players,nothing will make them give him out to any of the teams in the premier league,they will rather prefer giving him out to Bayern Munich that are also knocking.
Manchester United are in need of a regular goalscorer,but if I were Ten Hag,I will consider using Rashford to be my top striker in the middle of the park,and use Antonio and Sancho at the wings.I believe he won't be able to get a quality attacker in the transfer market,therefore he should make use of the players he has at the club ,than looking outside for a player that cannot deliver the way the club wants.