If you fart away every pay increase with lifestyle changes, then yeah, you'll end up as pinched on 100k as you were at 40k.
Agree with this. My DH earns a very very high salary now - but hasn't always. I earn 18k / year part time and am super frugal - I grew up in a trailer (not in the UK), some periods with no food etc, so am a bit traumatised by this.
When we married 25 years ago DH had a $15k credit card debt and a dodgy job, yet my fear of poverty put us on the straight and narrow and we locked it down while his income increased skywards.
We are now late 40s and very comfortable as we didn't fall victim to lifestyle creep. This is the key!!! We have a paid off mortgage, zero debt, own a car outright, I have always shopped at Aldi, we have healthy investments. We save 70% of our monthly income - some for investments, some for hols, some for doing up our house.
Our only real luxury is my 2 DC go to independent school.
I have to say it has been a bone of contention a few times in my marriage. My DH understandably wants to have a big blow out every now and then. But we have always been happy with the basics - focus on the mortgage, don't spend more than you earn, don't fall victim to keeping up with the Joneses.
I say all this not to brag or go on all "look at me" in a Mumsnet way, but to demonstrate that a life of sensible choices can pay off and allow you to sleep at night in rough seas like this. Lots of people we know would be shocked if they knew how wealthy we actually are. I am grateful for the security every single day, in particular at the moment.
I still worry about putting the heating on however, ha ha! Old habits die hard.