... you buy knives with the express purpose to turn around and resell them at a profit, on a regular basis, then you just might be a dealer.
... you buy knives at wholesale, then turn around and sell them at just below retail, then you just might be a dealer.
... you have a store, or a certificate of resale, and are selling here as a Gold Member, then you just might be a dealer.

We're getting reports of at least 3 individuals listed as Gold members engaging in this sort of thing. Needless to say, this is frowned upon and will get your Gold Membership pulled.

Just a friendly warning from your friendly forums Administrator.

Kevin