"But we all know that nowadays it is the changed subject line of an email response in a thread... which is why it gets the attention the author mentions."<p>No, I think many people are aware of the broader definition.  Reading this and other comments here, I was expecting this to be a spamming tactic...but the email in question is sent in response to an active request for information.  "Re: Klein SDK pricelist request" is a perfectly honest and understandable subject line.