The hardware is cheap nowadays compared to the software. Any sub-1k dollar/euro PC will handle most things one would use Autocad for. It's the software that is expensive.
For a lot of the workloads a sub 1000 PC is enough (I'm in the AEC software industry and am quite familiar what we are talking about).
Take into account that most software in the domain we are discussing is decades old. Some things would work just fine on the lowliest PC you can buy from the cheapest vendor. And yes, sometimes even the most beefiest machine is not enough.