I looked this up. 250 words per page is considered to be the standard accepted number of words per page. So, three standard pages are about 750 words. Of course if hadn't been available, I would've totally found a way to prove that 249 words per page was the accepted standard. It really just comes down to the fact that this amount of writing feels about right. You can't just fart out 3 pages without running into your subconscious a little bit... 750 words takes a bit of effort, and it never fails to get me typing things that I have wanted to articulate without realizing it. And that's the point.