I currently do not see it worth merching items below a threshold price, a stone block can be bought for 2 and flipped for 500% and yet it's still not even worth thinking about when items like compass wood is bought around 600 and flipped for 200%. An issue is weight limiting potential of merching cheaper items in bulk which I believe ruins the depth of the economy.
example prices (I don't even think you'd get that lucky on stone blocks)
Stone block buy 2
Stone block sell 10
Stone block profit 8
Stone block margin 500%
Stone block weight 1
Stone block profit per weight = 8
Traders snow full profit = 6,400
Compass wood buy 600
Compass wood sell 1200
Compass wood profit 600
Compass wood weight 2.5
Compass wood profit per weight = 240
Trader snow full profit = 192,000
If there is no comparable profit between these two items, who is going to bother moving them between ports? if the answer is npcs there is an issue I believe.
Items need to be more competitive rather than having single items standing out in terms of moving cargo for profit between ports. I understand an argument to this is having different tiers of items but it's very easy to reach endgame resource merching which I believe is compass wood, also there are so many items in the 1-40 price range which eliminates a lot of items.