I work in the aerospace industry, mainly to satellites these days but I’ve worked in launch in the past and have plenty of friends who have as well.
That 450 figure is probably all of Falcon 9s development which has gone through several design iteration cycles. Industry rumors point to a new Falcon 9 booster being around $50 to build and a million or two to refurbish on average. The re-use is saving them a significant amount, but the upfront design cost was just so stupid high.
It’s also worth noting that Starlink supposedly launches at near cost meaning little profit for each of those, but then SpaceX turns around and prices Falcon 9 close to Atlas V for government contracts (90-150m total price so probably 60m profit) and gouges people on Transporter (they’re almost certainly pulling in 150-200m on each of those)
Carrying forward technical knowledge is definitely a big help. I suspect that’s why Atlas V was able to pay for itself because the booster was so similar to Atlas III which itself was similar to Atlas II.
The satellites I work on play this game constantly. Mission A and B both use the same underlying tech that needs to be developed, but mission A is first. So we charge mission A with all of the cost and then mission B looks a lot cheaper on the books