It's an individual's call, for sure. That's why I said "would I buy one", the emphasis being on it being my view. I'm not suggesting others necessarily would, and certainly not suggesting they should, see it the same way.
There's certainly a right/wrong way for me, but I'm not implying criticism for those that see it differently, and even for me, the reason it's wrong is at least partly pragmatism. .
I remember having a discussion with a friend many years (probably 10 to 15) about second-hand values. Specifically, we were talking about used camera gear, like lenses, and how it often made sense to buy 'used'. A lot of camera gear seems to hold it's value pretty well, or at least, the prices people advertise it at do. It's not quite so clear whether they get it or not.
I said I wouldn't pay anything like those prices for 'used' gear, and he told me my expectations were unrealistic. But it wasn't that my expectations were unreaslistic, as I knew full well what stuff was avertised at, and probably achieved. It was just that given the consumer rights thing, the fact that many warranties don't transfer (though some do) and the fact that I've seen how some people treat their gear and when you buy second-hand you usually don't have any idea whether the seller has treated his or her) stuff well, or very harshly.
For a CPU, was it installed well? Did it have a good cooler? Was too much, or too little, thermal compound used? Was it in an occasional-use system for lightweight tasks or has it had the nuts worn off it in 24/7 mining ops? And so on.
Unless the seller is known to me personally, that is a set of questions to which the uncertainty means I wouldn't even consider paying anywhere near that price, for a fairly high value item. Had it been a toy at, oh, £20, I might take a punt. But not on a fairly expensive bit of high-tech kit where the brand new, known retailer price difference is as small as that.
At least part of my rationale is hassle-avoidance. Yes, if it's broken, or maybe fails very quickly, you can send it back but even if that succeeds, you have the hassle of the mucking around, and potential disputes, in doing it. If you buy 'used' on eBay and it lasts 3 months, 6 months, then dies? Good luck with a dispute.
Hence why my friend and I disagreed on what lenses, etc were worth used. His point was that's what the market will bear. And that's right. It probably will. But that doesn't mean those lenses are worth that to me, because I'd rather buy brand new given the modest price difference and have a better chance (but not zero chance) of problems, and be in a much stronger and therefore less hassle position, if you do get problems. And if I can't afford brand new, then I'd question whether I should be paying 70%, 80% or 90% of that price for used, or not buying at all.
It's why you will very rarely catch me buying stuff second-hand at all, and if you do, it's very likely it's either because I know and feel I can trust the seller, or because it's a low-value item and worth a punt, or because it's something simply no longer available new. Or all three.
But of course, YMMV.