The goods price in the fief you're trying to sell is probably above 15.
S&D:
there is a general missunderstanding in that, pls dont quote that thing.
all buy/sell no matter the price are 1=1 S&D, u can test it yourself in strat, what that quote is actually explaining (in a confusing way i agree) is the replenishment of S&D in the fiefs.
So I am trying to sell goods at Aldelen, it has 177 atm and I have 200 and I am trying to sell 177, when I press sell it says You have sold the goods but I still have 200 even if I try to sell 1 it doesn't sell it?
U have to look at how much S&D the fief has and not the goods
buy/sell 1 good = 1 S&D.
when there is no S&D left u have to wait for it to go up again each hour or just move on to another fief wich has enough S&D.