For most practical applications, computing performance plateaued around 2011. Just look at how many people can't/won't use Windows 11 just because their ancient relic otherwise still works perfectly fine.

And if you want a source, anecdata is I'm posting this from an i7 2700K (aka Sandy Bridge) machine.

I bought her a t420, which cost less than $100. All I did was swap in an SSD. But here’s the thing, I bought two t420s, and when one breaks I cannibalize the other for parts, or just swap the SSD into the old machine. I make sure to always have a spare machine, which is not hard because after you cannibalize one machine, and get a replacement, the parts on the cannibalized machine will often suffice for a while until you need to replace the same part again.

For her use cases, and to be honest 90% of people’s use cases, a t420 from 2011 has an excess of power. And the peace of mind knowing that spilling water on the keyboard will be a repair that takes 10 minutes (I could probably repair a t420 blindfolded at this point) and effectively only cost you $10-$20, is wonderful. I’ve been able to walk her through repairs over the phone.

I tend to use old various X220/X230 thinkpad as beaters. Used to be big on the X201, but somehow the X201 has been creeping up in price. Yeah, I use and like my big M1 MacBook for work. It’s nice for what I do at my job. But in my personal life I’m 100% happy with Arch Linux and i3wm on a stack of thinkpads. Having swappable batteries might be my favorite part, other than how well Linux runs.

I've had a few of these over the years that I take to coffee shops/bars to work. It's nice not to feel nervous about a $1000+ investment just because the server is coming around to refresh my water.