The west isn't that rich anymore - I think it's mostly an artifact from only taking western things into account. The numbers would look very different if the methods weren't biased.
Yes, it's also a difference in values and culture, we are fools to think that Azerbaidjan would desperately need expensive weapons in their recent conflict against Armenia, when in reality they'd always prefer a dozen saffron tea cups over a thousand mortar shells to shoot towards the Nagorno-Karabakh.