Again, nothing to do with struggling to make ends meet. By going further with your argument you aren't fully comfortable until you can cover any possible event that might happen, since a dire enough event will exhaust any possible amount of savings you could have unless you're a billionaire. Medical emergencies and car crashes are covered by insurance for nearly everyone, if you make that much money I would think you have appropriate policies in place.
Ah I just realized you're in the UK. I'm also from the UK but live in California.
Now it all makes sense! I agree that 4.5k after tax is fine to live on in the UK. Here in the US where a carton of basic eggs cost $6+, a box of standard brand milk costs $4/5, that $2.5k is going to disappear pretty fucking quickly.
I was astounded at how expensive it was here. Even in London, you could buy Warburtons for £1.30 or so back when I moved a few years ago. 1L of Cravendale (I liked the good stuff) was still £1 IIRC. Now it's like £1.30? Still, way cheaper.
I don't think you have kids (especially infants/young ones) because in a high cost of living area, 2.5k a month is HARD. You can do that in Europe, not in the US.
Those situations also happen, they're not black swan events. My current medical plan for my family has a deductible of $3k. Every year we end up hitting that number. That's excluding the actual premiums which are deducted from your pay. Do you have ANY idea what you're talking about?