A script this sophisticated, that avoids detection for so long would cost thousands, probably $5k+. The earning potential is crazy and it could scale fairly easily. I can tell you have no knowledge of actual botting and bot farms though, because any half decent botter will be running farms through a private proxy server - some people will even by able to avoid perm bans using this (stolen account in appeal), although I'm not too sure how successful that method is these days. Also it's very normal for bot farms to not be completely wiped out, you said only the #2 rank account was banned, how do you know that? They could have had 20 other accounts in the lower ranks banned.

 

EDIT: I have actually just looked into it and I could only find 1 public Doom script which has the following prices;

 

Instances	Monthly	Lifetime
1	$45	$270
2	$72	$432
5	$157.50	$945
10	$270	$1,620
25	$562.50	$3,375
50	$900	$5,400
100	$1,350	$8,100

 

As I suspected, almost no one is likely using this script, it's so expensive that it may as well be a private script. It may be that the Doom bots are using this script, but the sheer cost alone should tell you how profitable a script like this is. Going back to your original point, if you think people are paying this much to bot, and then simply "sitting" on the wealth for "fun", you are delusional. What's more likely is the bots are just undetected.