We often see "backwater" (Africa, areas around the Indian Ocean, some parts of South America, etc...) areas of this world using 40+ year old aircraft and the tramp freighter still is in use in those self same areas. They are increasingly rare, but they still do operate.
First up, I should make note of
Mariner, which is Ian Absentia's development of Trav for the modern day.
Secondly, I'd note that the areas using cheap ships and aircraft are relatively dangerous, and to really make money you have to smuggle stolen, restricted or illegal goods like drugs and firearms. To my mind, this is a fine example for a
Traveller campaign - scrape together 250,000-1,000,000 for a ship, do a lot of dodgy work, watch out for drug-crazed pirates, and so on.
A lot of the idea of making ships expensive, apart from a feeling of realism, is that if you don't, everyone will be flying everywhere all the time. But it's not true. Nowadays, if you can afford a mortgage on a good house in a good location, you can afford a secondhand 1,000t general cargo ship.
Already in our modern we find that second-hand general cargo ships are available for under a million bucks. For example
this one is US$1 million, 3,200t, and built in 1970. This
nice old clunker was knocked together in 1975, 1,057t and was going for $330,000.
So if second-hand ships are cheap, why don't more people take up a life of carting freight? Because it's a hard business. Most of the work goes to 100,000t bulk cargo ships, or huge container ships. It's the same reason supermarkets killed the corner store - not because corner stores are expensive to buy, but because supermarkets had economies of scale and could squash the little guys.
As anyone who's bought a crappy car knows, you may save on the purchase price but you have to spend on the maintenance. And for ships there are crew, and fuel, and so on.
Here's an article discussing freight rates for shipping, and we see that we're looking at amounts like a thousand or few for each container. Even with just five crew at only $100/day each (cheap Phillipino or East European merchant seamen), travelling at 10kts cross-Atlantic you're looking at 14 days with the turnarounds, $7,000 just for the crew. A 1,000t ship might burn $1,000-$3,000 of fuel each day, so that's another $28,000. Your cross-Atlantic voyage just cost you $35,000, even without any payments on the ship or maintenance costs.
Then there's insurance - as the article notes, this might be $200/container cross-Atlantic, but if you want to head into the Persian Gulf or off the coast of Africa, it might jump up to $1,000 each. And you
want that insurance, because if you lose the cargo you have to pay the owner for it, and the cargo will be worth much more than the freight rate for it. So that's another several thousand gone.
Small freight is no way to get rich.
Now add in the dangers of piracy, weather - each week one ship of significant size is pirated, and a large tanker or container ship is sunk each month by storms, and the smaller the ship, the less resilient - well, it's not an appealing life.
Now translate this to space travel where the dangers are considerably greater. I mean, according to LBB1's character generation, on a 4 or less on 2d6 - 10 in 36 times - a merchant spaceman dies in any four year term. That's 28% every four years, or 7% a year, not far off WWII cargo ships out of convoys.
You really don't need starships to be tens of millions of credits to put people off buying them and starting trade. Just put in the normal lack of profit and great danger, and that'll do it.
