depends what you mean. If you think of it as a "replacement" of another launch they could have sold, then yes, it's the same cost. Lost profit opportunity is lost profit is a cost.

But if it means they can increase the # of rockets they build, they might pick up some efficiency gains on the back stretch. I'm pretty sure they're already struggling to keep up with demand, tho.

They're getting to the point where they're demand-limited rather than supply-limited - plowing through the backlog quite fast, and the GTO launch market is in a downturn.

SpaceX keeps rockets other customers "paid" for after they've landed (the customer pays for the flight, not the rocket). They've amassed a fleet they never had to pay a dime to construct.

I believe they have eight block 5 Falcon 9s that landed successfully. More if you count previous generations, but those likely won't be reused.

Does the price of a launch completely cover the cost of construction (excluding R&D)?

It does, for the competition, and there is no reason for SpaceX to go much lower as long as they don't build excessive overcapacity that needs to be filled.

Yes. They actually improved a lot of rocket construction and that's why they were cheaper then everybody else BEFORE re-usability. Now re-usability they just increase the profit.

Until somebody else challenges their price, they can get huge profit from every launch.

Not if the opportunity is to be ahead of your rivals to a new market frontier and guarantee a head start

Even then you're trading one opportunity cost for another.

So then make the competitor pay for it: each time they launch for a competitor, add a margin equating to the total cost of deploying a Starlink satellite.

Of course there is a markup.

They can build their own rockets

In 2040 after billions in investments.

They could create an electronic payment system to raise capital for their rockets.

And before we jump into this rabbit hole, yes, they can totally fund their own payment system with $4K and a small yellow pages startup. :o)

SpaceX was launching Falcon 9's 8 years after they were founded.. 2030 should be achievable.