Exactly. They don't need to sell at cost, they just need to slightly underbid the competition. Which they've executed perfectly. EU has no flying rockets right now and Ariane6 is basically DOA if it ever gets over the finish line. ULA has launched only 3 rockets this year.

SpaceX has eaten the entire western launch market by simply pricing their launches slightly below legacy prices. And at the same time they give themselves (starlink) the at-cost price so no one can compete with them there either.

Maybe Jeffery Bezos and his deep pocket book will eventually present some competition, but Blue will be fighting headwinds the entire way down to the bottom price. SpaceX has this down pat and BO will be learning on the go. Any price improvement BO makes for years to come can be matched effortlessly by SpX.

The only other plausible challenger is China, but those launches are not really available to the west.

Don’t forget Rocket Lab.

RL's current offering is a smaller rocket. There are a handful of small launcher companies out there, but I was talking about the launching of big payloads. Rocket Lab has plans to enter that category too, but hasn't flown anything yet.