It's not even just that it's cheaper to launch, but the full reusability and planned ability to refuel in orbit really make it a game-changer. A fully fueled Starship in LEO can take a huge payload to the Moon, Mars, etc and ideally land itself, potentially refuel in-situ and get back to Earth. They can make minimally-customized modifications for tanker Starship / Lunar Starship / Mars Starship / etc and it's like a space swiss-army knife.
Just look at the National Team / Dynetics HLS proposals with a bunch of expensive, novel custom hardware vs. Space X proposal which was "basically just Starship". It could obviate a huge amount of resources being poured into one-off disposable space hardware and let us instead focus on actually doing stuff in space.