And why should some people pay more than others for the exact same service ?
Because our society is set up to enforce massive income disparity. The available choices are limited: Reduce income disparity or kill all of your surplus peasants and impose enough fear on the rest.
If you don't do both those things and you don't make any attempt to reduce income disparity at all, eventually your peasants will successfully revolt. Of course, you'd have to have already got rid of democracy so they can't change anything that way.
What happens now is that income disparity is inflated even further, then reduced a bit by income tax bands. It's like a business that wants to sell a sofa at £1000 briefly advertising it for sale at £1250 and then advertising it for sale at the £1000 price they always intended to sell it at and proclaiming that it's for sale at at 20% discount.
You shouldn't complain about having the best of both worlds (massive income disparity and a large peasantry that isn't in revolt), nor should you complain about
not selling that sofa at the artificially inflated £1250 being taxed a bit more on your "income" that was already inflated to take that into account.