Import duty is the other solution, but that's illegal within the EU - the whole point is it's an economic union.
Theoretically it should be balanced out by workers moving to more prosperous parts of Europe (where there are more jobs) - and the treaties do specify free movement of labour. I don't know whether we've yet seen an influx of Greek workers moving to Germany, though.
There were lots of Germans moving to Spain and other places, when they still boomed. Lots of them are coming back. So in a sense you already see an influx of workers from Greece to Germany, it's just that they are German.
Theoretically it should be balanced out by workers moving to more prosperous parts of Europe (where there are more jobs) - and the treaties do specify free movement of labour. I don't know whether we've yet seen an influx of Greek workers moving to Germany, though.