I've had, at one time, close to 2 billion legit in items and pure. This was based on the market then, not now. It would be quite a bit more now. Legit as in, I didn't use programs or hack accounts. I just have big name friends with the ability to influence and notify me when things were going to rise in value. Or drop for that matter.
Overall, close to 3 billion. Its really easy to make neopoints, more difficult to keep them I suppose.