In one instance (on the video), the app consumes ~20 MB/min while idle (not logged in), and ~33MB/min when logged in. You can watch the video where I show this consumption. I've experimented and recorded the network traffic. I've recently figured out that WhatsApp consumes too much data and since I'm using my phone's data, how much it consumes matters. Sometimes I leave WhatsApp on for many minutes (guesssing here up to 2 hours).
I often use my phone as hotspot on my laptop and use WhatsApp desktop application.
