The trade off to killing merchants is the loss of merchant, like how killing Griff camp early pretty much screw your build until you get to the seeker camp.
The reason we feel like it has little to no consequences is because half of the merchant NPCs will end up dying so you might as well be the one to kill them. If you start killing merchants in seeker camp as well, then that is something to consider but before this hotfix, the seeker camp is the location where you actually start losing tons of money because of how expensive purple/unique gears are compared to what you loot. Shamefully, because Act 1 ended right after that point, you never get to see your 10k gold stash run dry from buying level 10 gears.
