That sounds like an exaggeration. He's not a Golf Digest top instructor, he doesn't teach at a fancy club in LA, seems like he recently reached a pinnacle by being featured on the Me and My Golf youtube channel, not the Golf Channel.
Gankas may be coming onto some people's radar just now, but long before he was featured on a YouTube channel, he had a very large Instagram following that included other influential instructors. Some the techniques he popularized (alignment stick placed across the arms at the top and dropped during the pivot) was "borrowed" by TV instructors as was some of his lingo.
He's been teaching Wayne Gretzky's son for a while and one of his juniors made it to Augusta in the Drive, Chip, and Putt competition. He also teaches Sung Kang (PGA Tour) and was instrumental in getting his student Johnny Ruiz onto the Web.com Tour from having no status just two years ago.
If that amounts to 300-400 an hour, I'm afraid to ask how much Drew Steckel charges