It looks like this isn't just iOS and iPadOS, but also macOS. In that case, there is plenty of software that fits that bill, such as Maya and Avid. I'm sure there's mass media, banking, video game development, and lots of other software that costs near that, or will some time in the future.

Even if it were just for iOS and iPadOS though, they do want iPad Pro to compete with desktops in places where expensive software runs. For instance, Grass Valley Livetouch could be done on an iPad.