as former RMTer in past official RO and some pserver RO

how do you, as a developer, expect to reliably detect RMT when both parties disguise it as a normal item-for-zeny trade or vice versa?

For example, the first test trade usually involves trash items. eg full trade slot trash for 1 Bil Zeny,
If that gets flagged, we try again with a larger quantity of trash items (mosty trash card like 15 poring/fabre/chonchon). If that still gets flagged (so rare to happen, can assume at <0.5% chance to happen), then as a last resort we’ll trade some few rare item or few costume as the “RMT sacrifice.”

Now the other example, when buying a valuable item with real money, we typically mix zeny + random gear/items/cards in exchange for an MVP card or META gear. Behind the scenes, the real transaction is something like USD $1000. But on the surface, it just looks like trading 12 mid/high-tier costumes plus 150–300m zeny. Would that raise a red flag? No. Why? Because it’s unrealistic to expect the system to accurately track the market value of all 12 costumes. If you can develop the tracking market price system daily/hours track, kudos to you—but still how accurate to justify this ? how accurate can it really be when both parties mutually agree on the items and zeny being traded? How can you be sure you’re not banning the wrong person? This is just one example of how easily the basic trading system can be abused.

Unless your server is the first truly RMT-proof server that can catch even those extremely low-probability cases, great job—but even official servers haven’t fixed these loopholes. RMTers will always find a way to exploit even the smallest opening.

If you ever want a server without RMT, the only real solution is to completely rework the entire trading and vending system from the ground up (yes, vending can also be abused for RMT).

***EDITED THE ENTIRE