That was written prior to DeepStack being included as an option in
Blue Iris. Things are constantly changing. With the latest generation CPUs you can live without a dedicated GPU card, but with older CPUs, like a 6th generation, a GPU makes all the difference in the world when using DeepSack both in detection time and, as a result of faster detection times, better detection accuracy.
The problem is that it takes a GPU with 1000, or more, cuda cores to work really well. Between crypto mining, chip shortages and bots snatching up every card possible to make money re-selling them, the cost of cards is sky high right now. The old GTX970 I'm using is worth more now than when I bought it.