Irrespective of what Inno say the reason is why they nerfed the trader, to try and put a positive spin on it, the real reason is the same thing they did with the fighting, to stop expansions. So they nerfed the fighting to a point where its pointless for a lot of players (other than tournaments), so what were people left with? negotiating. They then also doubled/tripled the cost of negotiating to deter expansion. But many players then started producing more goods, build wonders to boost production, participated in the tournaments to increase their boosted relics. So still older players carried on (maybe a slower rate) expanding, they use the trader (as everyone has to) for the goods they need. As I've said before I am stuffed with coin mostly, and every 9hours I'm getting nearly 2m in coin. So to stop this expansion too Inno needed to make the trader much harder to stop expansion. Now this is an inconvenience to the older players as we have much more resource free than the younger players, but its a killer those younger players. Being in a fellowship helps but doe snot solve the trading issue. I have a very active fellowship in terms of trading, and I'm lucky that those in my 'hood' also trade, but I still need to trader to supplement my shortfalls.
I think they should have thought this through better, it wasn't liked on the beta forums with players much older than us, and clearly was going to be even more ill received here.
Inno made the change to limit the expansion of older players, so they should have left the trader as is for players who are younger, and factored in the qty of goods a player has in their inventory before changing the goods/coin formula. *number plucked out of air* So if you have <200K of each resource you are fine, but once you start having more than 200K of a resource then the trading price increases to deter hoarding, wont stop it just make it harder. This attacks the real issue and leave the standard gameplay as it is for the majority of users.