Is this really an AWS issue? Sounds like you were just burning CPU cycles, which is not AWS related. WebSockets makes it sound like it was a data transfer or API gateway cost.
Neither the title nor the article are painting it as an AWS issue, but as a websocket issue, because the protocol implicitly requires all transferred data to be copied multiple times.
I disagree. Like @turtlebits, I was waiting for the part of the story where websocket connections between their AWS resources somehow got billed at Amazon's internet data egress rates.