You literally said it yourself, reusable rockets are just so much more economical and scalable for future growth, building one extra booster to handle more launches is far easier than expanding production facilities to boost production by dozens per year and the associated logistics (Also, the price advantage is only in the small to medium lift range so you'd also need far more launches for the same capacity), all of that costs money, time and manpower. Unlike what people think even SOEs don't have infinite money, they're still budget and time constrained.
Also, you do realize Falcon 9 is extremely fat in margins right now, I wouldn't be surprised these new expendable rockets are launching at a bare profit if not break even just to attract more customers and put a nicer looking number on the brochure to keep themselves competitive which really isn't uncommon these days.
People at CALT and other launch providers aren't dumb, they ran the numbers and came to the same conclusion that reusable rockets is the future instead of trying to scale up production of these expendable rockets.
In the long term, reusable rockets are desirable, especially for progressively larger unitary payloads.
But dingyibvs is also correct in saying that if there are existing expendable rockets are also competitive with resuable rockets (like F9) in terms of payload to orbit, then it implies rocket quantity, materials, labour, etc are sufficiently plentiful and work well enough and can exist as a bridging capability until reusables become more prevalent.
There's no reason to contest this particular hypothetical, because the question isn't necessarily about what is the best solution for long term sustainable launch to orbit, but comparing specifically the costs to orbit compared to a vehicle like F9.
If one desires to more regularly send larger unitary payloads into orbit, then reusables are the only way forwards because the whole point of unitary payloads is many smaller rockets (resuable or expendable) may be able to put up the same equivalent mass and volume into orbit and perhaps even at equivalent cost, but it won't be a singular object.
