The board is not the expensive part. It's the getting reliability qualified and then having staff fit it to every substation, arrange the data links, and construct the dashboard.

I also wonder what the realtime requirement is. Data from a minute ago is fine .. except in this kind of situation, when things are changing very quickly.

The nice thing about frequency based regulation is it's an inherent property of the system, so as long as you're connected to the grid you've got the info you need to decide when to turn on or off.

If you're monitoring real time power consumption you then need a whole extra infrastructure to communicate this info back and forth. Of course you then have to consider how you're going to keep that extra infra online in the event of power issues.