It makes me sad how there's such a trivial way to wipe out gold sellers and their bots without requiring any appreciable manpower or coding, yet it doesn't get done.
In case any of the ZoS support folks happen to see this and want to pass it along, here's how you do it:
Add a new entry to your accounts database called say "GoldSeller_ID"
Next, have any of your staff log into the game and find an obvious farmer bot, and give them a unique ID in your GoldSeller_ID entry for their account.
Once you've done it, you have a simple script that does two things:
1) Any time an account with a GoldSeller_ID # trades with another account, either by sending mail with attachments or a direct trade, you also assign the GoldSeller_ID to the account they traded with.
2) Every so often, the script automatically suspends at random roughly half the accounts with a given GoldSeller_ID assigned to them.
** It's important not to ban all of them - because you want to leave them with some accounts they'll keep using. They'll just try to make some more accounts for their bots and money mules, and the moment they pool their gold / collect from their farming bots, you automatically get all of these accounts flagged as well. ( I would prioritize the banning accounts with the highest amount of gold on them, to destroy their stock effectively, however. -- if they lose their entire stock of gold every couple hours, it will rapidly become unprofitable and at least some of them may give up)
Since the farmers will periodically consolidate enough gold onto a few accounts to use for sale, you'll be able to spot all of their accounts rapidly. Just by flagging one single bot, in short order you'll have flagged their entire money mule network and any players who've bought from them.
There's no way the farmers could keep up with making new accounts, since your script will automatically tag and suspend (or just outright ban) them. You don't even need any manpower for this, other than the simple task of identifying one of their accounts initially.
Anyway, use this as you will. With a minimal amount of effort you can have an auto-ban system for gold farmers. All it requires is you to identify one of their accounts and it does the rest of the work for you.