IMTU, 2Td is the "standard" for crews, not 4Td. Why? Corporate ships cram crew into as small a space as doable without them going insane. (And US Navy praxis shows it's a survivable rate, as does the HG crewing allowance.) It's not comfy, but it's good long term.
Passengers, however, need that extra space. Ever spent a week entirely inside a hotel room or a trailer? I have. With good company, it's fun; with bad company, it's hellacious.
Oh, and NASA puts 7 people in 71 cubic meters.... just over 5 tons... but the training and testing for that is rather rough. So I don't feel bad at all about using 1Td per crewman on designs where I think I can get away with it logically.
All this sounds logical and plausible, but the salaries that starship crew commands suggests that they have something going for them. Maybe it's a sort of guild thing instead of a union. Or perhaps something akin to the massive autocracy of the British Jockey Club. If a captain ships unauthorized crew, he gets blacklisted, not only by other crewmembers but by shippers, maintenance workers, stevedores etc. If a crewmember works with a blacklisted crewmate, he gets blacklisted. If a company employs a blacklisted captain on one of their ships, they get blacklisted. If a shipyard works on a blacklisted ship, it gets blacklisted, and so on and so forth.
Anything like that would be a time-and-space specific rule rather than a generic rule, of course.
If the ship is tied to a particular world in such a way that sanctions can be imposed on it (or its owner), contracts that made the captain liable for the return fare of anyone discharged on a foreign world and the salary payable in any case, would prevent anything like that. Tramp vessels I'll grant you.
Once more showing that crew (and passengers!) must have something going for them since they get a full 4T apiece to enjoy.
(Mind you, I just can't believe that passengers aren't allowed to travel double occupancy and that some wouldn't want to do so if it cost them roughly half the standard fare).
Hans
The cost of DO is significantly more than half of SO.
The share of the steward doesn't change, nor does (except under MGT) the cost of LS per person. And that accounts for about 1/3 the cost of a passage; the other 2/3 are the cargo loss and infrastructure, which does scale. The exact ratios vary from system to system... But DO should be about 65 to 70% the cost of SO. I've shown the math on the boards for HG, MGT, and (during the playtest) T20. (Yes, the numbers for DO pricing in T20 are my fault...) I've even worked them out for sublight travel (posted over on
rpgg.)
Why 4Td per passenger? It's a good amount of space. It's a little more than a singlewide trailer shared by 4 people, or a camp trailer (8'x20'x7') for one. It's just enough space to work out, stay healthy, and have sanitary and food prep facilities that a person not trained for it can cope with.
As for crew getting 4Td? Do they? Not in HG; only officers. MGT allows doubling crew up, too. Bk2 allows it for non-commercial ships.
Civil crews, especially tramps, need to do something to keep the guys aboard; passenger equivalent quarters are a good start, especially if the quarters are effectively "home." Given that a 15' wide singlewide is about 14 Td, and are rated for a family of 4, one can see that 3.5Td per person is a sufficient long term rate if they have something to do outside that space.