How would you calculate travel costs in slips, that the PCs have to pay the NPC? I counted the squares from fragment to fragment multiplied by 10, but then the PCs know the distance.
Not specific to your game, but I took a look at a brief summary of it to get an idea of what it was about.
That said, in other settings and games where travel fees are based on distance, there are still other factors to consider.
How nice are the accommodations? Private staterooms and catered meal service are going to be expensive, while a hammock strung between two girders in the cargo hold and only-whatever-food-you-brought will be cheaper.
How safe is the ship? If the ship is carrying all the latest emergency gear, it's going to be more expensive. (Hidden gatcha - if they remove some of it to make more room for people1, it could be expensive and unsafe.)
How safe is the route? If the destination is through commonly traversed lanes, it could be cheap because there's no need to worry about (and arm for) pirates, or it could be expensive because of the
bribesfees paid to make it so. If the transport may need to fend off the government, that's an expensive issue, too.
How regular is the route? If you want to get somewhere exotic, someplace that few people have reason to go, the trip is going to be more expensive.
How legal is the voyage? If you want to go somewhere that people aren't generally allowed (or the passengers specifically are not allowed), you need to hire a particular type of ship. Even if you're going someplace that's legal in general, if you need
illicitspecial landing privileges or deliberatelyaccidentally erroneous paperwork, it'll be more expensive.
- What are the passengers supposed to contribute? If the passengers are nothing but paying cargo, the price is going to be more than it would be if they're expected to contribute to the voyage - a skilled chef could agree to prepare meals, an engineer could offer maintenance services, performers could offer entertainment for the crew, etc. Favors payable on arrival are also a possibility.
- Haggling can cause the started quoting price to be higher than the owner is willing to sell passage for, with the expectation that the passengers will try to get a better price. The carrier should, of course, have an absolute minimum price he's willing to offer passage for.
In short, even when distance is a primary cost motivator, there are numerous other situations that can affect (potentially drastically affect) the actual cost of the trip.
1RMS Titanic, I'm looking at you.