A random thought on Germany and Greece.
If apple producers and banana producers have the same symmetric Cobb-Douglas preferences U = A0.5.B0.5 the competitive equilibrium has half the apple crop being exchanged for half the banana crop.
But if the apple producers only like apples, and refuse to eat bananas, the relative price of apples (Pa/Pb) becomes infinite, trade stops, and the utility of banana producers falls to zero. The apple producers become infinitely rich, if we measure their income in bananas. The banana producers have zero income, if we measure their income in apples.
If we tax the apple producers, and transfer T apples to the banana producers, the relative price of apples falls to (Pa/Pb) = B/T. (Because that's the banana producers' ratio of Marginal Utility of apples consumed to Marginal Utility of bananas consumed.)
Suppose the apple producers are more patient than the banana producers. So at the same rate of interest, the apple producers want to lend, and the banana producers want to borrow.
If the banana producers borrow T apples from the apple producers, it has the same effect on (Pa/Pb) as a tax and transfer. (Pa/Pb) falls, which makes the banana producers have higher incomes measured in apples, and the apple producers lower incomes measured in bananas.
But how will the banana producers repay the loan? Here's where it gets interesting. What's possible for one is impossible for all.
An individual banana producer can always repay his borrowed apples, provided some other banana producers continue to borrow apples from the apple producers. He sells some of his bananas to buy apples from those other banana producers, and uses those apples to repay his loan.
Similarly, an individual apple producer can expect his loan of apples to be repaid, provided other apple producers continue to lend apples to the banana producers.
It is possible for each loan to be repaid, but impossible for all loans to be repaid. Each borrower and lender must get out of the game before the game stops. I think there might not be a rational expectations equilibrium with borrowing. But it must look very tempting to individual borrowers and lenders.
Do Germans like eating Greek olives?