If TO ever PLAYED in EvE then he MUST have seen what troubles can bring PLEX like system.
Like i've seen so many threads about ppls sell Plex in trade contracts for (rough trivia) 400 mil credits.
Ok yeah fine you buy it for 400 mil credits !BUT! here's a huge CATCH! In trade contract can be traps like:
1st step - you buy plex
2nd step - you send your money AND plex you bought back to the man who selled it.
And here can be the end - you lost money AND plex you bought.

And about gil sellers... I'll never risk life of my account by buying money from poor korean childs who have no life... I prefer spent my time in game and, !yeah!, grinding money by myself...