If you have small pre-defined sets of events in data structures that compress well. That is not the case for any real system.

> And so of course if you have to optimise things, you would need to drop some information you pass to the events, but you would need to do the same for metrics (reduce the number of metrics emitted, reduce the prometheus labels,...).

Those are entirely different orders of magnitude both when it comes to size and how much usefulness you lose. In modern storage backends like Victoriametrics a counter gonna cost you around byte per metric per probe. And as you emit them periodically, that is essentially independent of incoming traffic

Capturing the requests into event/trace/whatever other name they gave to logs this month is many times that and is multiplied by traffic.