The easiest and simplest solution is to just enable an anti-spam feature like the one you get in wow through an addon called BadBoy.

It blocks everything related to gold and website links in the chat by using a word filter system. They just need to add gil/www. .com @ /service and so on.

Such a feature imho should be a standard feature in any mmorpg.

It's sickening the way they let these scumbags ruin their game by not doing anything to prevent them from spamming.