The figure I heard was 90 a year. Either way, it's not many.

The problem is that the military-industrial complex is designed to make money, not win wars.

It's all about selling the "latest, greatest" new toy for as much money as they can get away with. Of course, it's too expensive, so politicians penny-pinch to cut the quantities ordered, forcing up the unit price still further. At the end of a short production run, the assembly lines are shut down and the experienced workers let go. Then, a couple of years later, there's a new "latest, greatest", so the old ones get scrapped or poorly mothballed (to save the maintenance cost, and because "they are hopelessly out of date"), and the whole cycle starts again.

Meanwhile, places like Russia and China work differently; they'll make a robust machine that is "just good enough", set up the production lines and just flex the quantities up and down according to the situation and budget constraints. So when a war starts, they just have to ramp up existing production lines with experienced labour already in place. They're already set up for scale, and any profits are purely derived from overseas sales.