you could not do that, as all transfers go through the internal market. no direct transactions or transfers. And I'm not confusing anything, just showing that there's a lot worse happening, just in case you didn't know.
It's been going on for many years, and the game is fine, but people are freaking off that some player might make some money selling crystals instead of CG, and that's gonna break the game :D
In store, 16500 crystals go fo 100$. might take a beginner up to 1 year to farm that, at current crystal drop rates. It's not gonna break the game, I'm pretty certain.