Although it is kinda superfluous, cause when you're done with a dungeon you're heading back to town anyway so there's no need to store the loot in the stash. Useful for commodities, but the profit margins aren't big enough to warrant that activity honestly.
???
The profit margins on commodities is a 100% if you sell to the right vendor:
Beer/wine/cider go to the inns at Brynn, grain goes to the bakery in Brynn, salt goes to the spice shop in Brynn, char coal and timber go to the rotating elf/dwarf/Nistrian vendor at the docks.
You buy those commodities for 200 gold each and sell them for 400 gold each in Brynn.
If you look at your map, you will notice that each town that gives out contracts is surrounded by places that sell commodities. For example, near the Rotten Willow Tavern you can buy char coal and timber. So, when you go there to do contracts, you also buy commodities and then return to Brynn.
The supply of commodities is sadly limited (replenishes after 24h-72h), however, you can easily get five pieces per stay at a town (=3 contracts) at 1000 gold and sell it for 2000 gold in Brynn. That's a quick 1000 gold profit.
If you're super smart, you get the trade preference upgrade as early as possible. In addition to the 1000 gold profit, you'll get 200 reputation points in Brynn along with it. And that every time you go to Brynn in order to sell you shit.
You should be going to Brynn regularly anyway in order to exchange the Ancient Coins at the bank. The conversion rate is 4 pieces of gold per 1 Ancient Coin as opposed to 2.5 gold per Ancient coin you get from regular vendors.
Also, the money you get for gold, silver and jewels at the jewelry in Brynn is significantly higher than even from vendors in towns at Respect.
Plus most of the upgrades aren't really useful in the early game. They're a late game quality of life luxury (apart from the stash space and the workbench for fodder crafting).
As
jackofshadows already mentioned, you can convert food to fodder whenever and wherever you want using the Crafting skill which you start the game with: