They seem to be more common on the westcoast, and they seem to be more rare on the eastcoast.
To add.... It's not like there are many datnoids or NGT at LFS in Los Angeles or San Jose region. Don't get me wrong, it's more accessible but not necessarily easy. I'm there a couple times a year for vacay and my LFS runs. I've seen more "Asian Jardinis" or Fly River Turtles than I've seen NGT.
I know NGTs are not of a high demand than "Golden Jars" or FRTs. I assum that ITs and NTTs r easier to sell than NGTs. Since NGTs will get a higher price.