Ok, what if you discover an error after you have spent 2 hours exporting a video for YouTube?
You correct it in 10 minutes and then your machine is locked for another 2 hours. If you were part of a production house that would be totally unacceptable.
It worked for you because you don't seem to have a deadline or clients expecting a finished product within a set timeframe and the next job waiting to be completed.
Generally Adobe has poorly multithreaded optimisations for most of their filters, like capping out at 6 cores for specific workloads but then single threaded performance becomes equally important.
If I do product shoots the "hero shots" will usually be made of anywhere from 20 to 50 RAW images that need to be focus stacked and that takes a lot of computational power (and RAM).
From a production point of view the cost difference from $8k to $16k isn't much. If it enabled you to finish tasks faster they would go that route. He also needed to pay you for your time, which would cost a lot more yearly. If he could cut your salary by 40% by going with slightly more expensive machines he totally would.
If he needed that many machines he probably also had enough work to gain from faster processing and finishing the tasks quicker.
Everything else in the production were more expensive, from camera bodies, lenses, lightning, studio, tripods, dollies etc.