Not everyone, and in fact the majority of people, don't purchase imports or export. Done properly, only the affluent actually pay the tax, most likely making the average closer to 1 credit per person.
3000 Billion credits over 272 worlds makes 1.1~ish billion credits per world. After paying for bases, logistical points, and other militarized shore facilities, we should have about 500-800 MCR in ships per planet average.
Of course, the source of my conjectures come from the average import/export taxes paid in the British Empire in the 16th-19th Century. Using Terran historical data lays me open to the normal "this ain't Earth, and is in the Far Future" assaults, but in a small ship universe the regular trade will not be in bulk consumer goods or bulk foodstuffs. It will be in luxury stuffs for those that can afford it.
Toss your tomatoes. My logic works. It works easier if the pops are controlled as well, but it works.
First, a math issue: 3000 billion divided by 272 comes in around 11 billion, not 1.1 billion. 3000 billion credits in an Imperial population of 300 billion is ten credits a head, not one.
Your logic works; it's the numbers we're quibbling over. As they say, the devil hides in the details. Britain had imports of around 10 million pounds (the currency, not the weight) in 1760, roughly an eighth of their GDP, against a population of around 8 millionish and at a time when a pound was 2-3 weeks wages to a laborer. I don't know what the import tax might have been overall, but if it were
only 1%, that still would have come in over 0.1% of GDP - in Traveller terms, quite a bit more than a single credit a head. I suspect it was quite a bit higher, but they were in the midst of the Seven Years War, so it is likely unrepresentative. As you point out, it's vulnerable to criticism on the "this ain't Earth, and is in the Far Future" basis.
At any rate, I really think 1 credit per person per year's very low for a sector that's fought five wars. I'd really consider 10 to be the low end; that's the price of one ordinary quality meal, per year.
As to your estimate of base construction : a 5000 dTon ship with a crew of 40 is coming in around 3.3 billion credits, over 80 million credits per crewman. My guess is base construction's going to come in a
lot lower than 80 million credits per sailor occupying the base. What I get is the ship costs 3.3 billion credits; the crew costs - what, a million credits a year, maybe two? - and there'll be maybe one or two personnel ashore in support roles for every one aboard ship (current USN is 317 thousand personnel with 124 thousand aboard ship), so say triple that for total personnel costs; then shore installations and orbital installations.
The Free Trader's supposed to be good for a 40-year mortgage, but let's say very conservatively that our ship's good for 10 years. Means 330 million credits annually for the ship, maybe 5-6 million for the crew and support personnel. Orbital installation's hard to quantify - they sure don't need jump drives and jump fuel, but they do need things a ship might not have like major repair machinery. Still, you don't need a repair drydock for each and every ship - most ships will do with a place to dock and someplace for the support crew to live. But, let's play conservative and call it 1:1, give us leeway for shore batteries, annual maintenance costs and things we haven't thought of.
Okay, all told then, our ship's costing us somewhere between 400 and 700 million a year - possibly a good deal less if a ship lasts longer than 10 years. Your 3000 billion budget (10 credits a head annually) buys - at its most conservative - five thousand 5000-dT ships if a ship lasts 10 years, plus an equal value in orbital and shorebase construction. More likely 7000 to 8000, and possibly double that if we decide a warship's good for 20 years in service. .
Is still a lot of ships.
