When you go into a trade with this person, he is going to tell you that they have a team with developers which are working constantly and doing everything. Which is a lie, he just does everything to tell you a price over 1000$ so he can say that this is a "premium" product and asking you to pay either all the money or just half of them. When you pay he just blocks you from the server and steals the money.
Which is exactly what happened to me. He is a scammer and not a developer.
Here is some proof:
I paid him 800$ which after that banned me from the server.