That's a very worthwhile point but there are a few major reasons why it's a more problematic strategy.
First, reliability. When you engineer a vehicle as large and as complex as an orbital launcher which only operates once in its entire lifetime you typically need to over-engineer a lot of key parts of the thing in order to ensure a high level of overall reliability. This runs counter to the sorts of optimizations necessary to bring production costs down by orders of magnitude. More so, when a full up test inevitably results in the destruction of the vehicle (because it is expendable) and tests cost as much as a launch (tens of millions of dollars) it makes it very, very difficult to evolve the design of the vehicle extensively.
That leads to a catch-22, you have to run a lot of launches to make the vehicle design significantly cheaper to manufacture. Buuuut, now you've vastly increased the development cost of the vehicle so you've erased all of the cost gains you've made.
But, if you design for reusability then you can actually increase reliability because the cost of the vehicle is amortized over multiple flights, so you can have a more expensive vehicle.
Also, while a lot of aerospace components (like fuel tanks, electronics, etc.) can be mass produced with the right design, this is a lot more difficult with rocket engines which have a very high number of precision machined parts made out of special alloys. This makes the engines the long-pole in the costs of a rocket, and it's very difficult to reduce those costs. Right now SpaceX is already the world's largest manufacturer of high-power rocket engines, so if there was a way to cut costs on them they would already be on top of them.
Now, back to reusability. Another thing that you get from reusability is that testing can be much cheaper, since you can make incremental changes to a vehicle design and then re-test it.
With reusability you have the best of all 3 worlds. You have reliability, you have low per-flight costs, and you have an enhanced ability to prove out potential vehicle redesigns economically.
Now, if the size of the launch market were much larger and reusability were more difficult then the equation could change, because it might be easier to recoup expensive cost-saving efforts over a shorter period of time.
First, reliability. When you engineer a vehicle as large and as complex as an orbital launcher which only operates once in its entire lifetime you typically need to over-engineer a lot of key parts of the thing in order to ensure a high level of overall reliability. This runs counter to the sorts of optimizations necessary to bring production costs down by orders of magnitude. More so, when a full up test inevitably results in the destruction of the vehicle (because it is expendable) and tests cost as much as a launch (tens of millions of dollars) it makes it very, very difficult to evolve the design of the vehicle extensively.
That leads to a catch-22, you have to run a lot of launches to make the vehicle design significantly cheaper to manufacture. Buuuut, now you've vastly increased the development cost of the vehicle so you've erased all of the cost gains you've made.
But, if you design for reusability then you can actually increase reliability because the cost of the vehicle is amortized over multiple flights, so you can have a more expensive vehicle.
Also, while a lot of aerospace components (like fuel tanks, electronics, etc.) can be mass produced with the right design, this is a lot more difficult with rocket engines which have a very high number of precision machined parts made out of special alloys. This makes the engines the long-pole in the costs of a rocket, and it's very difficult to reduce those costs. Right now SpaceX is already the world's largest manufacturer of high-power rocket engines, so if there was a way to cut costs on them they would already be on top of them.
Now, back to reusability. Another thing that you get from reusability is that testing can be much cheaper, since you can make incremental changes to a vehicle design and then re-test it.
With reusability you have the best of all 3 worlds. You have reliability, you have low per-flight costs, and you have an enhanced ability to prove out potential vehicle redesigns economically.
Now, if the size of the launch market were much larger and reusability were more difficult then the equation could change, because it might be easier to recoup expensive cost-saving efforts over a shorter period of time.