Thing is, when I WAS a high earner, I thought the same, that I wasn't well off. But I was. Living in the same town on £12k is far far harder than it was on £45k, even when you bear in mind that I got some benefits when I was earning that.
The benefit top ups I got when I earnt £12k did not take me anywhere close to the £45k I had previously earnt. In fact even with 3 DC's to pay childcare for, I wasn't hitting £19k. And childcare in this town is criminally high, and at that time 80% of it was covered by benefits.
So I still had less than half the income to pay the same (well, actually more) costs.
It still took the same amount of food to adequately feed my DC's, and that still cost the same amount of money.
You can't say that it costs someone earning £12k less to live - it doesn't. It just means that they have no luxuries, where someone who is on £60k does.
It may not SEEM like you do, but in honest terms, having a car, or even two, IS a luxury you can't afford when earning £12k. If that means you can't take a job that requires a car to get to, then you can't take that job. If that means you can't try to earn more, then that's what that means.
I can see through my own life experiences just how easy it is to be so blinkered that you cannot see beyond your own life, and to realise how lucky you really are to have those choices. But you are lucky, and you do have those choices.