please, start actively fighting off bots, as things stand right now (3 euros = 1 mil) buying directly from them nets way more value than buying your own battle pass.
Heck, even buying kinah from them and then buying Siel from players makes it cheaper than buying it directly from the store, don't you see the irony?
The economy is heading towards people that buy from them only (manastones being 100k each and enchantment stones being 400k each).
As for how you fight them, there is mostly one way: make it not profitable for them.
Having servers with virtual machines online 24/7 has a cost, having Siel to farm has a cost, if you start actively banning players that buy from them, you discourage the proccess because: players will be scared to lose their account -> they will think twice about buying -> gold sellers will have less consumers (thus less profit) -> they also keep getting banned (thus losing Siel money and resources) -> eventually it becomes less profitable or nets losses -> they leave.
With the current economy, where one hour farm nets around 300 - 500k, a legit player will struggle to do anything because prices will keep inflating from people that buy Kinah from sellers (heck, a single player that invest 100 euro could wipe out the entire broker from key items).
Please, do something, even if you have to hire an FTE for this it will eventually net you more profits (cause a well managed game with a positive press gains players overtime, instead of slowly dying to a bot ruined economy and over-priced under-valued cash shop, which will generate a bad press).