ZeniMax Online decided not to create an auction house or any serious trading system into The Elder Scrolls Online. I’d say commerce in TESO is very Dark Ages, but the early medieval era actually had markets, traders and some form of organisation.
So it’s come down to players creating a system. A marketplace that doesn’t exist in-game, but in the TESO Elite fansite, devised by players. The official TESO Twitter account has endorsed the system, probably so the developers can get back to squashing all the bugs that have been plaguing the game since launch. It's an odd endorsement, though, as ZeniMax previously defended its no auction house stance by saying such things ruin game economies and trivialise getting good gear.
It’s a simple system where users make posts advertising or looking for specific items, split into the two mega servers. Purchasers can also give sellers feedback, so eventually it will be easy to spot who the most trustworthy traders are.
As well as feedback, a dispute system is also in place to handle problematic trades or unfair feedback. Mediators will also be added soon, and they will help facilitate trading and have their own feedback rating.
As helpful as it is to have such a system in place, it boggles the mind that it doesn’t exist in-game.
Some form of player market is just a basic MMO feature, a convenience found in plenty of MMOs where you’re not paying for the game and then dropping cash on a monthly subscription.
For a game that walks a path as worn as TESO does, it’s quite the accomplishment that didn’t bother with something so commonplace.