Omni–Crate Technologies have cornered the market in meeting your interstellar transport / container needs. They offer a variety of cost–sensitive containment systems to suit everyone from the Corporate BargeTrain runner to the independent far trader.
Starports, depending on quality, will have trade info for other worlds but the information will be rated by its age.
NorthStar will have a clockwork trade / cargo system running under the surface. Cargoes will come and go on routes on their own and prices will adjust accordingly. Finding rare pelts will bring big bucks — but sooner or later other ships will try to fill the need — if they can. A new biosphere will always be a treasured source of organic compounds and materials not easily or efficiently artificially made. So if you are headed back from the scatter with a load of rare goods in your hold and you pass a klick long fat-tran on its way out, you can safely assume you should try and make as much money off your load as possible because prices are about to plummet.
Your price for goods will be set by adjusting base price with your mercantile skill — the actual give and take process of haggling will be abstracted.
Gravlifters at a class Alpha Starport? groovyliscious. Assuming you are going to find one out in the Scatter when you have 25 tons of furs to load? Maybe not so much.
Taking on passengers is a possible source of income. As for how willing they are to interact with the crew, that depends on both their mission and how they came to board the ship...
The game doesn't work at that simplistic level of "planet X buys slaves". Outright old school slavery in any sort of near future human based space game is kind of inane. On the other hand, a contract to deliver guest workers to a project deep in the Scatter with a severe penalty for letting any of them "consider other employment opportunities" — a distinct possibility. As for welching out on a complex deal or delivery, you are free to do so and then suffer any consequences.
While fabricators exist in the game, we are not talking about a Star Trek style replicator as much as a sophisticated relatively solid state elemental processor / synthesizer / 3D photocopier. You need an aluminum oxide sealjoint for your towns MHD turbine generator – no problem. You expect the complete turbine to come out the other end of the fabricator – you will have a long wait coming.
These are useful as there is no point packing a few hundred thousand shovels from the start when a 10 cubic meter fabricator can churn them out from ore and organic molecules as well as forks, ladders, nails and solpanels. And a dozen other things a colony would order at the last minute.