"Hannah, how much do you think Daddy should spend on my birthday present?"
"About the same as you'd spend on me or Ethan."
"Ah, but he's known me longer."
"But mum, when you and Dad spend money on me or Ethan that's money from the joint account. Dad'll be spending money from his own account which won't have as much in it as the joint account so actually Dad should be spending less on you than you spend on Ethan and me."
"Ah, but what am I worth?"
It is at this point I realise I'm clutching at straws. I consider explaining that the joint account is actually a massive overdraft but decide against it and abandon the conversation and open a beer.