I used to work for a company whose licensing fees were mid-five figures a seat. Granted, not every person in the company needed a license; but nearly everyone involved in the production process did. The company also benefited from vendor lock-in, because skilled workers tend to get pretty attached to their workflows and competitors in niche software tend not to have 1-to-1 feature overlaps.
It seems like nearly every profession has high-priced software that's required: artists, engineers, accountants, lawyers, doctors/nurses, research scientists, architects, etc, are buying products from Adobe, Quicken, West Law, Reed Elsevier, Epic. None of those are small companies, yet all of them focus in somewhat niche information technology sectors. I'm struggling to come up with a profession that doesn't touch software anymore; even retail workers use point of sale and inventory software.
I do agree with your sentiment though. The software is expensive because it's so niche. The market for all of this stuff is pretty limited, meaning there's only a few products offered, and the capital required to build competitive products makes it prohibitive for a company to build their own. The companies making the software also understand their target industries intimately enough to know exactly what price the market will bare.
However, it does leave an interesting market opportunity for and engineer + domain expert to tap into the market with cheap, low-feature offerings. Or maybe we will see more companies bringing development back in-house.