Contract negotiations and signings between players and clubs, as well as between clubs, take place on the transfer market. In order to minimize costs and maximize revenues, clubs assign players financial valuations that are estimated to be as precise as feasible in this theoretical area. Jack Southworth's £400 move from Blackburn Rovers to Everton in 1893 was the first time money was exchanged between football clubs for a professional player......read more here https://www.newzurban.com/2023/09/10-most-expensive-transfers-in-202324.html