It is a scam; you will meet him at 3 different places, but don't get the option of turning violent (or threatening him to get your money back AFAIK). You can mindread him to learn where his secret stash is (IIRC a gold bag with a random amount of gold), but I don't recall if that can make up for what you pay him. In any case, once you have the battle tower, it is pretty easy to get gold, so 500 isn't likely going to make a significant difference.
Larian may not have gotten a publisher for Greece (various release dates and regions are listed
here).
