From my prior thread asking for help collecting data, this is what I have so far. I'd still appreciate any more info people can provide, in the $1M-$100M range. To provide info, make a new character/minion and equip only your weapon. Let me know the NW of the weapon and the PR of the minion. Don't equip anything else please.
$6075 = 456 PR
$90566 = 3843 PR
$161879 = 6088 PR
$207380 = 7488 PR
$444312 = 14004 PR
$602195 = 17927 PR
$614282 = 18218 PR
$1663377 = 40682 PR
$8369914 = 148640 PR
$115623383 = 1215209 PR
The 40682 PR weapon is a perfect fit with my main character. I took off his tattoo and katana and bow and arrows, leaving only armor (no room to take all of that off). This gave me PR / MPR: 40,212 / 39,364. I put on the $1.6M weapon, and ended up PR / MPR: 41,525 / 39,364.
Notice that the increase of 1313 PR is super close to the weapon PR minus MPR, which is 1318. So simply saying "PR added by a weapon is weapon PR minus MPR" isn't exactly correct, but it's still amazingly close. Maybe the armor is having some sort of effect. Or, in another words, your weapon allocation (in weapon PR) is almost exactly your MPR.
I'm not sure if I have any software that will fit a curve to these points but I'll see. Maybe something in OpenOffice can do it.