Lets take a look at some stupid shit you said
You said that £1000 for your chair is justified because millions were spent on designing it 30 years ago, even though, to me at least, I wouldn't buy that chair if it was cheaper than my Secretlab, because you're just assuming that everyone wants the same things as you.
You said that the lumbar support only protrudes half an inch, even though it doesn't (source: I own it)
You said the Aeron is a great chair because you can sit on it for hours and hours and it will still feel comfortable, and that the Secretlab is about instant gratification. That's not true. The Secretlab is designed to be comfortable for long periods of time, which all of the reviewers who I watched before I bought it said, and I can now say myself after owning it. So by your own definition, the Secretlab should be a great chair, right?
You think the chair will just fall apart after 3 years. Let's assume I take good care of it and it makes it to four years. If I bought 3 new chairs in 12 years, it would end up being £1050, which is only about £100 more expensive than the Herman Miller in the UK. That's about £10/year extra over those 12 years. So why should I care about your warranty?
And now your only defense is that I'm brainwashed? Like, even if I was, I'm comfortable as fuck right now. so whatever.
I'm fairly tall, and one of the main things I was looking for when I bought the chair was a tall backrest that I could lean right back in if I wanted, maybe for watching movies. I got that in the Secretlab. I wouldn't get that in your Herman Miller. That instantly makes your chair less valuable to me than mine. I think you need to understand that you don't want and think the same things as everyone else. Don't get me wrong, their are shit "gaming" chairs, but that doesn't mean all "gaming" chairs are shit. And I say "gaming" because it's just branding. And yes, £350 is a lot, which is why I actually did my research before I bought it. Honestly, you're the one that sounds brainwashed.