I know this is a senseless post but, I can't help myself. As a combat class i'm happy to see 500kcr in my bank/invent. but, I always knew that "crafting" is where the real money is at. I had absolutely no idea as to how much money a crafter could make until a crafter in our guild was approached by a CSR (customer service rep) in-game regarding the unusual amount of credits he has. Now without telling you his name and, I'm sure most of you won't believe this but... he had/has in excess of 300Mcr. and like you i'm sayin' "Bullsxxt!" ... well after a long discussion with our guildie/crafter it started to sound plausible to have that kind of money. He would in effect buy (100-300kcr/week) other guildies property lots which would give him tremendous power when a good resource cropped up. He would depending on the resource quality (and other stats) monopolize the entire resource area... I'm talking 30 harvesters at a time.
Anyway there is more to the story, like the majority of the land lots he bought were on characters that only lived on our server to pump up our city population (and we would return the favor on their server)... but, this is gettin' boring.
Suffice to say 300,000,000+ credits is the most I know of.