What2doNexon

Keeping the information secret is a lot easier than keeping the items contained. There's no benefit to a hacker telling people how to make a 300 stat item, but there is a benefit to one selling a created one, regardless of what his hacker buddies told him to do.

There are only 3-4 people confirmed to have the exploit.
They are all part of the same "team"
Obviously they all trust each other enough to keep the exploit within them.
Hackers aren't idiots who betray their allies at the first chance.