Silt Strider

Silt Striders are huge bugs that have been modified to provide travel between settlements in Vvardenfell. Generally speaking, each silt strider caravaner will travel to four other locations. Travel is instantaneous in real-time, but game-time does pass. Health, Magicka and Fatigue will all replenish themselves, depending on how long the trip takes. You'll probably need to take multiple trips to get to your destination. For example, to travel from Vivec in the south to Maar Gan in the north, you would need to go to Balmora, Ald'ruhn and then Maar Gan.

Although silt striders don't really involve bartering, it does appear to count. If you have exceptionally high Personality, the caravaner will shave a couple of golds off the trip price, so this may be where it's showing up.