They've always been workstation grade hardware because they've been designed for specialised tasks with certifications from software vendors and optimised for a strict subset of tasks. The previous intel systems had dedicated hardware for video (EG the T2 chip in many models doubled as a transcode processor), ECC Graphics RAM and were highly optimised 2D Image and Audio processing. Current ARM systems are highly optimised for high memory throughput applications and multi-processing (and the genius NUMA implementation in the M1 Max Ultra is a legitimately innovative piece of technology; the interconnect between the two domains being as fast as local node memory is a stunning achievement).

The reason Apple sell so many systems to business is because they're a good buy for business and price and feature competitive with other *nix systems like the Dell Precision, Lenovo ThinkPad or HP Z. Not checked the pricing on the IBM Power systems recently but I imagine those are going to be astronomically priced by comparison.