Centers of Trade's advantage is the Diplomacy drip, which is nice but somewhat redundant with the smaller drip from Saltern, and the pressures it'll put on our people to develop more advanced forms of trade.
Actually having the Saltern makes the diplomacy drip insane. By having both trait and saltern we immediately have a dominant trade production, giving us +2 Diplomacy Drip. We can increase the Saltern lead dramatically to an uncontestable level and add another +1 Diplomacy drip every turn by committing extra salterns. With an income of 3 Diplomacy every turn...we can basically finance all those inefficient but lucrative actions, especially megaprojects, via overflow power.
Look to our trade goods:
Dye - Leading, but not dominant. Improving this is cheap for us.
Textiles - None. Not much point in competing here, we can't match cotton and we don't have it.
Gold - None. Not much point competing here, gold is rare and we'd have to ramp up the gold production massively to matter.
Silver - Moderate. This tells us that at ONE silver mine, we're in the running, but need more to hit the top. Would prefer not to hit the top, silver mining is very polluting and so we have an intrinsic disadvantage compared to people who are willing to dump arsenic and sulfuric acid into their rivers.
Salt - Dominant. No competition at all.
Copper - See Silver. Except worse since everyone has it. Too much pain to compete with.
Bronze/Tin - Nothing here. We need to establish local production, but competing is pointless.
Iron - Haha not trading this.
Wine(
@Academia Nut is wine considered one trade good or are all alcohols under the same?) - Dominant. No competition for now, and difficult for the lowlands to catch up, because the soil is wrong for it. We can improve the flavor and variety well enough here to add diversity, because we're the only ones who make enough honey and fruit in the region to experiment with mead and ciders.
So off the bat?
We got the Saltern drip +1
We get bonus drip for salt and dye +2(?)
We'll be getting the Wine drip next turn +1(?)
What can we do with a passive income of +4 Diplomacy per turn?
Well, for starters, once we trigger a golden age, we could probably spam megaprojects like mad with this.
EDIT: Okay, less crazy than it sounds