To get those pesos to pay you back, he needs to get those pesos, which means selling you something and then giving back the money you used to pay for it, which

To get those pesos to pay you back, he needs to get those pesos, which means selling you something and then giving back the money you used to pay for it, which means the real interest you got was those goods. That's real value that diluting your own currency doesn't get you.