We hear this argument a lot. But what if you send people to Mars and want to provide them with electric power? Solar pannels don't work well on Mars because (1) the solar radiation is about 1/2 what it is on Earth and (2) because of dust. So you decide to send a nuclear reactor. Then you say "because he have a big rocket, our reactor can be heavy and cheap. Even a "cheap" reactor" costs a LOT more then a super heavy booster, hundreds of times more.
I worked for years at a company that did cost projections and project planning for what is now called "Space Force". Guess what was the major factor used to predict the cost of a payload? It was "mass". The cost to build a spacecraft is almost proportional to the mass. Why. Because if you give an engineer a mass budget HE WILL SPEND IT. It does not matter what the mass limit is, they will find some way to use all of it.
Cost is NEVER the manufacturing cost, that is nearly trivial. It is not the launch coast either as that is like 10% of the total. It is LABOR. If a mission takes 10 years to degin and fly you have to pay the engineers and scientists for 10 years. THAT is where all the money goes. If you fire them the mission ends. Even while the spacecraft is in coast mode to Mars, if the experts who built the thing leave the project, the project dies. You must keep the staff. OK not quite true, some staff turnover is allowable, people can retire and new hires can come up to speed but only at some reasonable rate.
In any case, heavier is not cheaper, it only saves some manufacturing cost, and that cost is already not the major cost driver. Design, testing and operation is far most then the material and machining costs.
The other argument is that Starship is not cheaper. It will take about 20 leaches from Earth to get one Starship to Mars. (most of the launches are fuel tankers). Then to get the ship back to Earth you need to somehow deliver a fuel plant and tank farm to Mars.
For round trip landing Apollo-style lander will be far less expensive, even if it leaves the landing stage on Mars. Starship is better if you are doing a one-way landing of bulk cargo
Power source?
Ignore the luddite nuclear phobia.
Small modular fission reactors will do the trick for larger systems and if you haven't heard, a chinese company is doing a relatively cheap Small radioisotope nuclear "battery" using scalable semiconductor tech. BV100 if you're interested.
And yes, Starship is cheap to build. And fast. So are Raptors.
That company you worked for was it a startup or Old Space working on Cost-plus contracts? (I used to be NASA myself so I know the difference.) And yes, labor and overhead makes the bulk of costs for Old Space. Not so for commercial space startups.
For the startups (and SpaceX which is still in startup mode) pricing and accounting is more like the auto industry than the M.I.C. model.
Automation, AI controls, and additive manufacturing cut costs something fierce. Look at SpaceX staffing levels at the star factory, ignoring the construction crews, and remember where Shotwell earned her stripes.
The entire Starship business model is similar to the Air Force's replicator project: "Quantity is a quality all its own." Or Anduril's. Last century rules don't apply.
New Age, new rules.
SpaceX isn't building 2 ships a year like ULA, they're building two starships a month and ramping up to build two a week. Some will be reusable, some will be expendable, some will be custom single-launch space infrastructure (fuel depots, telecopes, orbital transfer vehicles, habs and orbital labs/factories). The Star factory is modeled around the Tesla Giga Factories for volume production, much like the Starlink satelite factory that cranks out over 120 satellites a month and is ramping up to sell backbones and customization services for other New Space companies. Modular design for mass production.
So what if it takes four V3 tanker launches to refill a deep space Starship? The tankers will be cheap *and* reusable so the only cost will be the fuel and oxidizer and spacex is already building an air liquefaction plant and a Sabatier plant is next.
Don't fret overmuch about Mars, anyway; Mars is aspirational and easy to pooh-pooh but the real impact of Starship in the next decade is cislunar. Now, if Psyche does turn out to be loaded with heavy metals, that could change. But otherwise the value of Starship is 200+ Tons to LEO at maybe $10 a pound operational cost.
New age, new rules, new math.