Yeah... when you buy stuff, you lose KILL PTS and FLAG PTS proportionnaly (I guess), so by losing Kill points, your 'total kill points' used in Rating formula is affected ; so is the 'average points per kill', which affects directly the AVE. AVE isn't really Average bounty per kills I guess... more like average points for kills (with current settings, you get 1 pt per bty of your opponent, so they're the same ; except in the case mentionned above)