With 20 Dt cargo and a subsidy, it becomes something like this:
A few things aren't adding up for your analysis of the design
you posted earlier up thread.
With a fuel purification plant, wilderness refueling will remove the fuel cost from the equation.
Life support is Cr2000 per person aboard every 2 weeks, not per stateroom (occupied or not). So if you've got a "one man scout" operation with no other crew aboard, you're paying Cr2000 per jump (for 1 person), not Cr8000 per jump (for 1 person and 3 unoccupied staterooms).
Crew salaries ought to be Cr3000 per jump, not Cr2400 per jump, to pay the salary of a Pilot (Cr6000 per month) who is the only required crew member aboard a 100 ton Scout/Courier.
Reduce the fuel cost by Cr2200 and the Life Support by Cr6000 while raising the Crew Salaries by Cr600 ... and suddenly you're looking at a break even under subsidy condition with an 80% manifest.
Also, you should be applying an 80% discount for volume production on the variant (so you aren't dealing in "one off" construction pricing) which has multiple knock on effects that push the whole thing towards being a profitable merchant.
Personally, I would drop the tech level back down to LBB5.80 TL=11 (so 20 tons of cargo with 4 staterooms of accommodations).
Of course, the REAL MASTER STROKE BIG BRAIN PLAY would be to use a LBB2.81 Standard Hull with LBB5.80 drives (you waste 1 ton while saving MCr18.1
![Astonished face :astonished: 😲](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f632.png)
in construction costs). Fall back to TL=11 so you have 19 tons of cargo capacity with 4 staterooms. Put the Air/Raft Berth back in and you've got 15 tons of cargo capacity (1 major, 1 minor cargo). That then gives you enough room to dedicate 5 tons of cargo capacity to a Mail Vault and ... voila! You have a subsidized starship which can reliably and routinely generate a profit (once you put weapons in the turret and hire a gunner) just from delivering mail around ... any passengers and cargo services become "gravy profits" on top of whatever you're getting from delivering mail.