1. Corporations are incorporated somewhere, I'm sorry if you don't like the nation state as the organizing principle of modern western society.
2. Third world countries would not lose all investment, foreign companies would still get their labor 50% off and companies often taut reasons other than labor costs as reasons for moving such as logistics or opening markets- plus indigenous companies could still make use of very cheap labor although they'd have a harder time marrying that ultra cheap labor to cutting edge design, technology, and manufacturing processes.
and oh yeah, circumstances don't matter as long as they have the right habits so any economy decimated will be sent "10 habits of the rich and successful" or "think and grow rich" or "rich dad poor dad" or one of the hundreds books of that ilk.
lastly, exponentially? are you sure? what exponential function are you using? are you calculating savings in transportation costs? have you included CEOs and other management getting less, have you thought about how if companies are not improving their bottom line by going for the cheapest labor they may have to turn their efforts towards greater productivity, increased energy efficiency, product quality and "R and D" ? wouldn't at least some offshore companies stay and pay a higher rate and wouldn't that allow those lucky few thirdworlders buy more goods and services or send their children to college? and wouldn't a labor squeeze allow workers in the first world countries to increase their pay somewhat offsetting higher prices?