My work machine is a 2015 MacBook Pro that's similarly configured to my home machine. Still runs great. They offered to replace it last year and I asked why? It's still able to do everything just fine.
I say this to back up something the author said - you don't need to be so extreme and buy a machine from 2006. Buying a machine that's 3-5 years old is still a good machine to run all but the most-demanding tasks. Even then I ask why are you running your most-demanding tasks on your laptop instead of a server or EC2 instance?
Bottom line - yes: you can save a lot of money buying older equipment.