This is of course not including the yearly Unity subscription, where Unity Pro costs $2,040 per seat (although they may have Enterprise pricing)
Absolutely ridiculous. Many Unity devs are saying they're switching engines on social media.
Developing a good and feature rich game engine which also runs performant is a huge effort. That alone can cost a good team 2 years at least. Even more if we consider todays graphic standards. That's nothing which smaller studios can easily deliver. So yeah, it's an obvious decision to buy a license for a proprietary engine, where a lot of work has already went into. That's just business and nothing crazy about it. Companies using services or products of other companies is pretty ordinary.