I came up with this simple idea. What stops people from borrowing money at a particular interest rate, then reinvest sum in (most likely) a bank which offers higher rates on deposits. Bank the margin. Scale up as much as possible.I know banks do this. The thing to note is that it has to be done across international borders which opens the transaction to exchange rate risk. Hedge against exchange rate risk. There will be transaction costs, but this should become negligible as one scales up.Your thoughts?