.11 isn't cheap to be honest for just a Full member. I've seen them go for .1 here and there due to the fact you can buy newbies accounts registered in 2011 or 2012 and just post to get the activity up
Date registered doesn't affect activity. It's all about posts + amount of times logged in over 14 day periods. There are some 2011 accounts I see that are now active posters but have very low activity for this reason. I think people just want 2011 accounts to look like old timers....
Yes If the account is 2011 -2012 that doesn't mean that you can post and boost up your activity fast, It also important that the accounts owner made at least 1 post per 2 week period all the time but if he didn't those 2 weeks doesn't count. So that means there are no Newbie accounts that you can get activity fast up, from Jr. Member yes there could be but rare situations because If people post in every 2 week period usually they make much more posts anyway.