Um, have you been reading the thread?
To say it nicely, some of them have no clue, while unfortunately others are straight out dishonest.
I can't talk about dealers outside of Crown Heights, but I know the dealers in Crown Heights personally (more or less), and my personal observation of them definitely plays a role in the trust I have in their word!
Going back to the original issue brought up in this thread, it was all about a different
class of Mezuzos, referred to as Mivtzoim Mezuzos. This has nothing to do with mezuzos sold to Anash for personal use.