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There's an interesting thread here about how trades are currently (v3.61/v4.00b) worked out, & why your station may stop trading for a time, with Dev comments/clarifications
Personal trading via capship
I'd prefer to leve leave this until v4 becomes live, but ATM (other than the standard buy low, sell high - & get your trades in first) smalltalking multiple NPCs to gain stackable discounts can work effectively. if a little tedious..
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As above, but there may be a few traders on the station that have different prices for their wares; worth checking if you want to buy a bunch of green marines or sell off your illegal wares from a distance!
Black market trader is not available in menu "Enter<Enter-5"5>, but still can be found in the NPC list that opens in details screen and can be contacted remotely. You can sale sell illegal wares while out of reach of police ships remotely.
All trader prices and inventories are randomized, so if you see 2 traders of same type, they will may have different prices. Sometimes you can buy from one and sell to another for profit without leaving the platform or station.
Each remote trade add adds a 2500 Cr transport fee.
High reputation with the trader faction 's Faction will give a discount on items . Discount for trader (capship or personal trading). A limited time discount for the individual trader or their station can also be achieved as Smalltalk revard.reward (discount variable on how far you succeed with the smalltalk minigame)