The reason will be that the older, less expensive Apple TV 4k will no longer be available. There's really no other reason. This is a price hike, plain and simple.

I need a new ATV to replace the ancient HD one that's dying in our living room. I've been putting it off because of laziness and now I can't get one directly from Apple if I don't want this too expensive, Siri-infested thing with all its microphones that I'll never use. Dammit!