The port at Devil's Ford is the location of a well-known horse market a few days' journey from Novigrad. According to Dudu, while it may be a very well-known market, it is not in fact the place to get the best price for the beasts as the merchants there tend to collude rather than compete. There are also the costs associated with organizing the market which are then factored into the prices of the horses, so a wise vendor would seek to sell his animals where horses were more scarce and fewer overhead costs... say, in Novigrad itself.
For example, a horse could fetch 90, or even 100 crowns at the Devil's Ford market but Dudu was able to get 130 crowns per animal by selling them at the port of Novigrad where only (rather slow moving) oxen were left to transport goods. In particular, an overseas shipment of pelts, while light, required rapid transportation to other markets. With all the other horses in town sent to the market at Devil's Ford, Dudu found himself able to name his own (decidedly better) price and realize a much tidier profit.
It was just one day's journey from the market that Dainty Biberveldt and his retinue stopped to rest for the night on their way to sell the halfling's horses. After an evening of drinking and merriment, everyone retired for the night but Dainty needed to relieve himself. It was then that he first came face to face with his mirror image and began his real financial education.