@V0ldek You missed maintenance and logistics. Military gear is typically amortized over a 30 year period, so a £3M missile might actually cost something like £0.3M to build then a bit under £100K per year to keep in working order (new batteries and motors, regular inspections and refurb, cost of the leak-proof warehouse it’s stored in, etc).
Setting up the infrastructure for that manufacturing is expensive and complicated, requiring supply chains and skilled workers. Even ignoring the risks of disruption by hostile action that’s a lot of infrastructure and industrial capacity to build up in an active war zone, and from the western perspective it’s better long-term to have that extra manufacturing capacity locally, to say nothing of being easier to sell to politicians and voters.
@YourNetworkIsHaunted Ukraine is building its missiles well enough even now, it has expertise, skilled workers, etc. Ever heard of Mriya, Antonov, etc?
Also, ironically, it was a major supplier of the Russian Air Forces, and it maintained Russian rockets until recently.