I'm wondering if some of this can be save specific. As in, the assignment of workshops to towns, is randomized (I did check for nearby competitors ofc). And then after that (AI) caravan setup and routes are randomized. That would be save specific. So which goods congest, and where, will be very save specific. It may work out in the later game, or not. This save isn't into what I'd call late game economics.
Prosperity and foot traffic feature heavily. But, so do wars. I think something is still off, perhaps in the larger balance of goods (and again, my perspective is map wide trading runs sampling all trade goods in the years just after prices should have settled). The AI choices on when to make war, how long, for what and when to sue for peace have been tweaked. This also is causing changes to demand.
So here is what I can suss out in my save after more testing, in general economic balance. With less wars, overall food prices start high (as all prices do), then settle, then generally start crashing map wide. Spot profits can be made, but more spot-based than before. Grain seems to crash first (great news for breweries?), since it is more map wide, but eventually the others do too. Luxury demand seems in line with past saves (wine, beer, linen, jewelry, etc). Other "gear" shops lack sufficient consumers. With "equipable gear", the prices seem set, so that isn't noticeable, but demand seems lacking. Wool workshops produce no output (verified by sending 100% to warehouse). However, the price of tools also crashes quickly after the economy stabilizes.
My feedback though that sorting this out isn't "fun" stands. I play random rolled characters for the fun of just a different life path. My 1.2.3 save is a no smithing trader. I'm not here to paint the map. The information is just too obfuscated in the UI (the why) even though the what is nicer. I do like the UI changes, this is gameplay. And with no control over your own caravan routes, or your second party it feels like the player lacks agency unless they are 100% babysitting that town and workshop. Warehouses do seem helpful here. It works, but again, my issue is "fun". And I usually like this type of run, and from prior runs I have a feel of how prices usually settle out once the "burn in" period is over.
However, I think there are other economy changes in 1.2.3 that need to bubble through perhaps a few saves. Have you checked overall map wide prices?