Here's what I found its empirical but can give insight
MuddyPaws said: ↑
Very true but the point I was trying to make is that for some users, iMessage could be a HUGE data user. You are right, it doesn't compress the video or picture. That's what I was talking about. A 20 meg video sends as a 20 meg video. A 1.8 meg picture sends as a 1.8 meg picture.
Wrong! iMessage not only does compress pics and videos, but it also reduces resolution.
I just sent a 48.6MB video over 3G...