I’ve updated my first response.

But as for looking at it in a Marxist way (obviously you are correct in that Marx did not mention unequal exchange, the chapter of Capital based on international trade never saw daylight and it is impossible to know what Marx would’ve written), Samir Amin came up with two accumulation models.

I have proposed two accumulation models, one involving the center and the other the periphery. The model involving the center is governed by the articulation of Capital’s two Departments, I and II, which, by that fact, expresses the coherence of a self-centered capitalist economy. Contrariwise, in the periphery model, the articulation that governs the reproduction of the system links exports (the motive force) to (induced) consumption. The model is “outward-turned” (as opposed to “self-centered”). It conveys a “dependence,” in the sense that the periphery adjusts “unilaterally” to the dominant tendencies on the scale of the world system in which it is integrated, these tendencies being the very ones governed by the demands of accumulation at the center…

These conditions, governing accumulation on a world scale, thus reproduce unequal development. They make clear that the underdeveloped countries are so because they are super-exploited and not because they are backward…

The “two models,” nonetheless, constitute but a single reality, that of accumulation operative on a world scale, and characterized by the articulation of Marx’s Departments I and II—grasped henceforward at the global scale and no longer at the scale of societies at the center. For the periphery’s exports, at this scale, become constitutive elements of constant capital and variable capital (whose prices they lower), while their imports fulfill functions analogous to those of Department III: that is to say, they facilitate the realization of excess surplus-value.