Just as many users (probably more) can attest to the accuracy of the usage meter when verified independently using built-in monitoring facilities of their routers and/or independent third-party applications such as Glasswire, Networx, BitMeter OS, etc.
Best bet is having a router that supports traffic monitoring since it will identify cumulative usage for all devices accessing it. Third party applications (in particular Glasswire) installed on each device give a more detailed view of how, when, and by what data is being consumed on each device separately.
Doing that will allow you to verify the accuracy of the Exede usage meter (or not as the case may be). In 4 years I've had exactly one instance of unexplained usage attributable to Exede.
Most of us who've been on satellite for years have simply adopted a trust by verify approach by seeking an independent second opinion.
https://myesvt.exede.net. There it will show you much is being used hourly, daily, also shows you what area is consuming the most of your data. The only thing I still haven't figured out, is what's considered storage? On my laptop a good chunk of that uses data. I've deleted unused apps and all games. We'll see what happens. Good luck and hope this might help a little.
I have to agree with Old Labs that running a program Like GlassWire will certainly provide some eye opening detail on what is running on a given computer. It will however only monitor the computer that it is installed on .. not "network wide". It can be installed on multiple computers of course and the data from each correlated but that still leaves us with potential usage by the router itself and any and all wireless devices.
Most users when faced with a data loss or data related issue are reluctant to remove their router from the equation during the opening troubleshooting efforts. That really complicates things.
A router however is at the heart of every network. Every Byte has to travel past that central point.
Some routers offer a Traffic Analyzer function that's allows tracking of data by device. Being able to look at your router and see just how much is being used by WHOM is a big first step.
Here are a couple of screenshots of my Asus RT-AC3100:
Details by device:
Once a device has been determined to be the culprit, nothing tops GlassWire in digging out the details of just what program or process within that device is using data: