I liked a russian hacker's story of building an IR camera by repurposing an old scanner: at one point he tries to source a detector from China but is unable to order it because of (he says) US export rules; then he remembers he's from a country that builds its own air-to-air missiles, and finds a Russian supplier who sends him the part...

I believe the rationale here is that if you can source some gadget from China, it's going to be ten times cheaper than any alternative, since there's an enormous stock of those there used to to make other gadgets, therefore low margins and high turnover.

So that's where you look first.

Yep, maybe GDP is not a great measure if one country can produce a box of cookies for $1 while another $4. Turns out physical output is important (bushels of wheat, pounds of steel, # of cars, etc).

But if a $4 country can produce an advanced military gadget but $1 country cannot, then the $1 country has a problem.

That's why difference exists in the first place - because of power imbalance driven by different levels of technological progress.

As we're seeing now, it's an even bigger problem when a country produces an advanced military gadget for $1 and the other country can't match it in terms of production for even $50.