I ran log
and grepped for "videosubscriptionsd" process. I found that it seemed near every log output for it there was Dropbox referenced either above or below. After stopping Dropbox, the problem went away.
Dropbox: (LaunchServices) [http://com.apple .launchservices.default] Local database thinks system build version is <private>, but the OS really is <private>.
Right above that I got this line:
videosubscriptionsd: Received distnoted matching event
And it was seemingly in an infinite loop. Thus I figured it was the reason for high CPU.
As soon as I stopped Dropbox the problem went away.
References: