I'm no advocate of either parts of the arguments but if blizzard wanted money, wouldn't they gain from banning people quite frequently? Since you get 30 days free with your purchase and after that it's pretty much free(since you buy gametime for gold). If you're not spending your gold on gametime for your bots, you're kinda doing it wrong aren't you? We all show how adamant we are with buying more accounts so they'll probably gain a lot by waiting until we add WoD/Legion and then killing the account.
And that's exactly what they are doing. If they banned more frequently, people would simply stop botting; meaning that botters wouldn't buy new licenses of the game, and wouldn't add to their numbers.
It's all the numbers game. Why would they ban 300k accounts for 6 months, and then for 18 months? Banning for 18 months is permaban with a different wording. Not even a handful of people will retake their old accounts after that time has passed. They either have new ones with actual gear, or have completely forgotten about the game.
So, why the 18 months instead? Well, a suspended account still counts as a playing or active account. A banned account, obviously not. Even with their new decision of "not telling the numbers", the second they'll have good news Blizzard will change his mind yet again.
Clearest example is Overwatch. Game is a success, so it is perfectly fine to share BETA PLAYERS (rotfl) and sold boxes. Numbers call numbers.
Back to wow, let me tell you...when you have 1,2...less than 5 accounts, maintenance is easy. If you like the game , you could be banned every month (that's an approximate actual duration of accounts according to the ban section) and still have made a profit a restart new accounts!
But that doesn't take into account :
1) Hardware ID flagging is not a myth. It never was, but it is that kind of thing that was so rare that, until it happens to you, you don't believe it. Now they are flagging systems. We don't know how, and finding how would be much more difficult than reversing warden. There are a massive number of ID's in a computer, and even a noob programmer can make a program that takes several of those ID's, encrypts them, and voalá, you have an unique ID that nobody (outside of Blizzard) can understand that it is being used to ID you.
2) 1 month is great. 2-3 months is still funny. 6 months with 5+ accounts, and it will become a job. Weariness.
3) There are additional costs that newer botterstend to overlook. Is your time free of cost? When you have fun it is great. But when you get bored, and you will, you'll expect to be rewarded for your time. Outside of maintenance factors as electric power, the computer usage, the handling of the chars and the accounts and the guild banks....
4) Eventually, if you are serious about this, you'll get a manual investigation. And then, probably all your guild banks, and all accounts related, even unbotted ones, will be banned. This have always happened to hardcore botters, who always considered it an added risk. But, with the lowering of gold price, the lower demand, increased ban rate, many big time botters have switched games. So, the gaze of Blizzards GM's is upon not-so-big botters now.
TLDR? wow botting for profit is as good as dead. Who knows what next expansion will bring...but with the current ban situation, it doesn't bode well.