They show that their latency has gone down, but that is not always the reason just because it correlates.

I would expect that most companies that both a) are big enough for the cloud providers to bother talking to and b) have proven they have the ability to run their workloads on multiple clouds are getting discounts from whatever cloud provider they end up using. One condition of these discounts might be that they can't publish exactly the prices they are getting, or any information that would let you infer the price.