My main machine cost about £600 back in 2011
It's had a couple of new drives and a new GPU since then, I put most of the cash into the motherboard and processor so it's aged fairly well.
The processor's an i5 2500k, easily one of the best investments I've made, 6 years on and still quicker than the average mid range processor. 3.7GHz stock, but does 4.5GHz just fine with a fanless air cooler.
It's single core performance is still up there with the best of them, which is useful for me as I use a lot of CAD and simulation software that doesn't really scale to multiple cores efficiently.
It's nice for the occasional big compilation too.
I don't play much vidya anymore, so the GPU isn't that useful to me, originally a GTX560, now a GTX970 bought from a housemate with more moARMney than sense when he upgraded to a GTX1080).
When I'm not at home I share the eternal comfiness of >>202
with a T400, though lately I've been tempted by the lightness and everlasting battery of a chromebook (Running Linux of course).
When I scrape some cash together later this year I'm going to have a go transplanting some modern low power silicon into an old T60 chassis.