Yes, they are. This isn't secret information.
ETA:
https://en.wikipedia.org/wiki/Falcon_9#Production
In 2016, they were producing 18 cores per year, with a production line that could work on 6 cores at a time. That means each core was taking around 4 months to produce. They may have cut that down a bit since then, but it's still a lot longer than 3 weeks. And production is easier to parallelize even for one rocket than servicing, so production is also likely to have a higher cash burn rate than servicing.
Or you need a slightly bigger rocket for the same payload. But not much bigger, because you only need a
small percentage of the fuel for return.
But it doesn't really work that way anyways. VERY few space missions (stuff like the ISS) involve multiple launches for one payload. Generally speaking, you pick the launch vehicle you need to get whatever your payload is into space. If one rocket won't do, you don't split it across multiple rockets, you just pick a bigger rocket. Plus, SpaceX offers the option to fully expend the Falcon 9 to get a heavier payload into space without re-use. You just have to pay more for it, because SpaceX doesn't get the rocket back. And that price differential (something like $60 million for reusable launch, $90 million for expandable) is another good indicator that re-use is economically viable.
And lastly, we haven't even touched on the advantage that re-use offers in terms of volume. SpaceX can launch many more missions in a year than the number of rockets they can manufacture. So they can operate with a fraction of the manufacturing capacity it would take to get that volume out of single-use rockets.
Maybe you haven't been paying attention, but I know that.
Not with great precision, sure. But again, time scales tell us a lot. The time scales indicate that reusability is efficient. And that meshes with other known facts, like the price premium on expendable launches.
Is it logically
possible that Falcon 9 re-use isn't an economic winner? Yes. Is that likely? No, it really isn't.