SLS is around $ 37000 / kg to Orbit
Falcon 9 is around $ 2700 / kg to Orbit
So in excess of an order of magnitude difference.
Starship build cost is currently estimated at $90 million [1]. Let's call it $100 million to make the calculations simple. So even if they can't reuse anything and the payload is at the low-end of what they expect, so 100t from the 100-150t range, that would be $1 million per ton or $1000 per kilo. So 1/37th of SLS even when fully expendable.
With full reuse, the cost should come down to around $10/kg.
Apples and oranges: a human-rated capsule is a significant additional cost.
Orion alone costs another $1 billion per shot [1]. Project cost is $21 billion.[2]
OTOH: "Since 2020, when Dragon 2 flew its first crewed and uncrewed flights, it has proven to be the most cost-effective spacecraft ever used by NASA." [3]
Nobody is arguing Falcon 9 isn't a good deal but you can't compare SLS to Falcon 9, the comparison would be Starship to Falcon 9, of which, Starship ain't finished! That's all I'm saying.
I just did, so you clearly can. And it is also meaningful.
In theory, a heavier vehicle should have lower cost to orbit, not higher, all else being equal, as some costs are constant overhead. And this theory turns out to be true when you have a comparable vehicle, the Falcon Heavy:
Falcon Heavy: $ 2,100 / kg to LEO (fully expended)
SLS: $ 37,000 / kg to LEO
Payload capacity is 68t and 70t respectively in this configuration, so pretty much identical.
If you only need 50t to LEO, price for the Falcon Heavy drops to $1,800 / kg as they can then reuse various components.
So SLS is already completely outclassed as things stand right now.
Then comes Starship. A fully expendable Starship, which they have pretty much demonstrated already, would be a further incremental improvement. Slightly lower cost, double the payload of Falcon Heavy, so around $1000/kg. Add even partial reuse, and you're probably in the $800/kg range.
And then you have full reuse, which they look to be close to demonstrating, which is a complete game changer. In the $10 / kg cost range. 3700x cheaper than SLS. That's two decades of Moore's Law kind of improvement. Absolutely crazy.
Human with food, water and air for a couple of days would be what, $5000?
Incorrect. I also compared SLS to both (a) Falcon 9 and (b) Falcon Heavy. Both of which dramatically outperform it in regular commercial flight.
Whereas SLS has had exactly one test flight.
And of course Starship exists. It has flown 5 times, which is 4 times more than SLS. And has landed both parts at least once, which is infinitely many times more than SLS ever will.
Kind of doesn't matter. There is no mission Falcon 9/Falcon Heavy couldn't do.
The moon architecture has been designed so that it requires SLS, not the other way around.
No rational planner would ever even consider SLS if they had a choice.
You would much rather launch distributed into LEO, assemble and go from there. The 2 billion $ a year could be spent on important things for the transition and the lander.
