Some collectors are honorable until it comes to that one special piece. Then they'll use anything legal to their ends.
What's a collector's best score? Taking for $20 in Grandma's pre-nursing home garage sale, that Scagel hunting knife she's had in the basement since her father died. That's a colector's dream, but still rips off Grandma who needs the money much more than the collector needs either their money or the knife. If you knowingly steal from a little old lady and justify your actions by "she should have known what it's worth" does that make you any less of a thief? Spread good karma, it might come back.
It's already been said, if you ask collector, as a friend, to buy a knife for you at a show, they'll do it unless the knife is so hot they want it for themselves. That's honorable?
How many collectors, when asked by a neophyte for an appraisal of a knife the collector lusts after, give a true estimated price? Or do they give a price think they can get away with to buy the knife?
Someone on this forum posted about how his dad taught him aboout the honesty of collectors and dealers. If I remember the story correctly, his dad gave him (teen) an antique pistol and sent him through a gun show asking people for opinions and prices, but not to sell. Not one price was correct, they were all low. Only one honest dealer/collector told him it was worth a lot of money and he should have it appraised by more than one person and sold proffessionally or at auction.
Honest collectors? Not when lust and greed get ratcheted up.