Not everybody will have the same experiences or opinions, but my thoughts are (from 1989, hence the amounts being less than mooted in PP):
a. 'Why would I give you pocket money? I don't care what the house looks like, I'm not paying for you to vacuum the stairs or clean the bathroom when I wouldn't do it myself.'
Vs
'I really appreciate you vacuuming, mopping the floors, cleaning the bathroom and kitchen and doing the washing up. Here's five pounds for doing all of that - if you cut the hedge each Sunday morning, I'll make it up to seven and a tenner if you run the strimmer around the back garden once you've cleaned the cuttings up. It wasn't getting done before, but it makes a big difference to the house.'
b. 'What's the point of taking all those exams? It's not like you're going to be a doctor. If you're lucky and find somebody who'll have you, you'll be married by 20. You can't work when you've got children - so make sure it's a rich man or you'll need to get yourself down the council and tell them you need a house'.
Vs
'I know everybody round you has got at least two kids by the time they're twenty, I was married at 17 after all, but you're smart and you don't have to do that if you don't want to. You could go to university and become a doctor, a teacher or a lawyer - or something else, maybe live overseas, own your own home and not be dependent upon anybody else. It'll give you the freedom to make choices throughout your life'.
Which leads us onto
c. 'Do what you want. I don't care what grades you get, you don't need exams to get a job in a shop or hairdresser's. Everybody else does it and it's good enough for them, why would you think you're anything special? I did fine working in a shop until I got married'.
Vs
'You could do really, really well if you put some actual effort in for 18 months. I value you and your potential and I want to give you an extra motivation - like if you were working, you'd get a payrise, a bonus or go up a point of the salary scale. How about twenty pounds for every B and thirty for As?' (or Cs and Bs as suitable for the kid's abilities).
One tells the kid that the effort and achievement is valued, one tells them that there's no point in bothering. I had the it's not worth the effort version throughout my childhood.