DD is going into y11 and last year I made a deal with her- every 9 gets £200, every 8 £100 and every 7 £50 (she's at a selective school- straight 7-9s not unusual). I've doubled the amount as a motivator for Spanish and chemistry where she's not trying and currently predicted a 5.
She told my SIL yesterday who said it's out of order but would tell me why she thought so. AIBU? I can afford it and DD is motivated by money. The grades are reasonable and obtainable for her.
SIL doesn't have teenagers so it's not a cousin comparison thing..