Not exactly, PCB assembly is super cheap everywhere thanks to propagation of chipshooters, what makes the cost go up is logistics - what do you do after you populate the board for your part? Ship it across the world, or to another factory behind the corner?
That largely depends on the size of your board and the total number you want to ship. As soon as you reach full truck loads or full container loads that additional shipping cost is marginal on a board level.
You are right in a certain way. What increases with distance is lead time and as result inventory. Both of which are off set by volume. Cross-border adds customs issues. Complexity is not that much of a problem nowadays, maybe it never was. You are right that all of this oblyakes sense with large numbers, small scale production is better done locally as a rule of thumb.
