Most of the activity in this field is grey at best and at worst illegal. You should steer clear altogether.
Especially with "bulk suppliers" who are actively seeking out 1000's of dollars worth of cards from a "long-term seller" at high discounts (I'm talking >50%), it is pretty much guaranteed that they are not in the legit business.
Watch out for these people on paxful too. If you use a highly discounted GC that proves to be stolen/hacked/carded and you use your address on the order, there is a real risk you'll have law enforcement knocking on your door. Check out some purse.io stories on reddit if you don't believe me.
I would not agree more with you BUT I am not asking for if its legal, grey or something else but the economy behind it. We cannot deny the fact that there is people with over 1000+ Gift Card trades (hundreds of them) and i highly doubt, they pulled of even 10% scams as you can only scam so much with one account. So I am not asking to ENTER that market, god no! Just to understand it.
Sure there must be someone doing this business and have an insight.
Someone sending lets say 0.01 BTC for a 200 USD Gift card for example, must have a way or know exactly, how to avoid being scamed. Doing it 1000 times in 1 year. People are stupid but nobody does a stupid thing a 1000 times if it doesn't work somehow right (i hope not haha)