Palace chairman Simon Jordan was angered by a Football League tribunal ordering Spurs to give a £700,000 down-payment on the 16-year-old but there are other clauses that could see the total rise.
The Premier League club will pay an extra £1.45million if Bostock makes 40 appearances for his new club and a full international debut.
Palace will also get a 15 per cent cut of any future deal to take the youngster away from White Hart Lane, with the fresh details emerging from a letter to a Palace supporters' group from the league.