Large advertising budget, as he pays for large display ads in Linn's regularly. He also sells on
ebay. Very high priced, at lease when it comes to U.S. singles. I've never purchase from him, and based on his past revenue listings, I likely won't any time soon.
Personal opinion: I find that most high-profile dealers that take out full-page and/or multi-page ads in philatelic publications tend to be the most problematic to deal with, have the worst or slowest cusotmer service, and are the ones most likely to have "issues" with their offerings.
That's just my personal opinion and experience. Others' may vary.