At 11, my DD had £5 a week, but we bought everything she needed, so it was 'frivolous' money and she spent it on sweets, magazines, plastic tat or saved weeks at a time for computer games etc
She is now almost 15 and she gets £20 a week, but has to cover her phone bill, going out with friends, gig tickets, merchandise, collectables and desired/fashion clothes and shoes etc (to be clear, we buy her clothing/shoes as she needs them but if she wants a £120 pair of DM's, she pays for them herself!)
We didn't pay for chores as I believe every one in a house is responsible for keeping the house clean and tidy etc, irrespective of age and incentive - it is simply a life skill that needs to be learnt
Children always have friends who get more. It's just life (not that they see it that way of course), I would add though that you need both parents on board with the ethos, otherwise it can lead to issues later on -bitter experience-