Endrick - €35m at 18. Move was agreed with the family when he was 16, but he didn’t move until he was 18, which is when the transfer fee was paid. Vinicius was similar and was €45m at 18. Rodrygo the same I.e. €45m at 18. Mbappe moved on loan at 18, and was signed permanently at 19 which is when the transfer fee was paid. The global record paid for a 17 year old is £25m for Bellingham, the global record paid for an 18 year old is €45m shared by Vinicius and Rodrygo. These are FIFA published records.
If he moves for anything over £25m before the middle of June, then he would be the most expensive 17 year old in football history.