I sold a few watches to a member here who turned out to be a dealer/flipper (has since been banned). Sometimes I got a fair price in sale or trade, but others not so much. Initially the story was often that he was buying it for himself or his wife and, "could I give him a better deal?" I didn't know he was a dealer. His technique to keep pecking at my price over and over to get me to cave in was done in a way to deflect that he was a dealer.
I'd sold him my Silver Snoopy Award for $14,000 cash (what I'd paid from money left after an accident settlement), because I needed money for a new furnace, hot water heater and Uncle Sam. After we verbally agreed to the deal, I then had other offers by PM for up to $16,500, which I had to decline because "we made a deal". He said he was so excited that he and his wife would have matching Snoopy watches, but then he posted it up for sale on instagram for $18,000, which I didn't know it at the time. IF I had known he was a dealer, I would have canceled the sale to him immediately, and sold it to the other member here who would keep it and enjoy it. I felt like I was taken advantage of. The "dealer" told me he kept my Snoopy in stickers and sold his, but only posted mine to "gain traffic to his IG account".
Around the same time I also sold him a Rolex Coke GMT II 16710, that I didn't realize how much the value had gone up since I'd bought it for $5000 a few years earlier. I thought he wanted it for his wife, and I traded it for $3000 cash plus a 3-year old 3570.50 with overnight shipping included, plus its box and papers from an OB. I think that he even sent me a picture of my old GMT on a red strap for his wife.
The next day I was contacted by PM from a member here, to be told that my GMT was for sale on OF for $8000. I was very upset that he was selling the watch at such a markup immediately after I'd sold it to him. He tried to make me feel better by saying he instead wholesaled it for $7000 because his wife decided she didn't want it, and that with overnight shipping of the Moonwatch included he'd given me $7000 in value and broke even (shipping did not cost him $500).
That was when I found out for sure that he was buying and selling watches for profit - it was easier to recognize what he really was after that, and later deal with him appropriately and not as an online friend who needed a good deal.
Meanwhile, my son still has not forgiven me for selling the GMT II Coke, which he coveted greatly and prayed to get for his college graduation. Instead, for graduation in 2 weeks he is getting a freshly serviced 3572.50 from his birth year, along with a gold capped Seamaster auto date dress-watch from my birth year. I think the GMT II Coke would have been a better gift, and I regret selling it to a flipper who hid his true identity.