My general reflex when it comes to any number of PC components, CPUs included, is to avoid the (very) highest end parts. This is for the well known reason that the top of the product range is where nearly everyone raises prices abruptly. If you want something close to the very best, the vendor will charge you for the privilege and the result is not that great a price to performance ratio. Going down a step or three can give you most of the benefits for much less cost. This is certainly the approach that I took with the CPU for my current machine, where picking an i5-2500 over an i7-2600 was about 2/3rds of the cost for much of the performance.

Well, you know what, this time around I'm not going to do that for the new PC I'm slowly planning. The lesser reason is that there is now much more of a (potential) performance difference in Intel's current desktop CPUs; an i5-8400 is clocked clearly lower than i7-8700, on top of not having hyperthreading and having 3 MB less L3 cache. But the larger reason is that I'm no longer convinced that economizing here makes long term sense with how I've treated my PCs so far. Specifically, I seem to get at least five years out of each one and I don't upgrade it over that time.

I think that buying a cost-effective CPU makes a lot of sense if you're going to later upgrade it to another cost-effective CPU when the performance difference becomes meaningful to you. But if you're not, buying a cost-effective CPU that meaningfully underperforms a higher-end one means that your machine's relative performance slides sooner and faster. Buying a meaningfully faster CPU now keeps your machine from becoming functionally obsolete for longer, and if you amortize the extra cost over the (long) lifetime of your machine, it may not come out to all that much extra.

(It's my current view that CPU performance still matters to me, so I will notice differences here.)

To some degree this contradicts what I said in my thinking about whether I'd upgrade my next PC partway through its life, where I was open to a mid-life CPU upgrade. There are two answers here. One of them is that I don't really want to go through the hassle of a CPU upgrade, both in figuring out when to do it and then the actual physical process.

The other answer is that this is all rationalization and justification. In reality, I've become tired of doing the sensible, economical thing and settling for a 'not as good as it could reasonably be' system. Buying an objectively overpriced CPU is something that I can afford to do and it will make me irrationally happier with the resulting PC (and the five year amortized cost is not all that much).