Comment by graup
Last time I checked (a few years ago), it was cheaper to send letters and small packages from South Korea to Germany than from Germany to Germany. The delay was also not that big (maybe 1-2 weeks instead of 3-5 days). I already envisioned an arbitrage business for this: a simple page where people upload their non-urgent letters as PDFs, and I just print and mail them from Korea.
This is already a thing; political parties sending out their mass mailings from Poland to Norway.