Imagine if we defined price stability as zero percent inflation in the euro area. That would mean prices would be rising in some euro area countries, but falling in some other euro area countries. It would mean that as soon as some products became more expensive, the prices of others would have to fall. Otherwise you cannot achieve an average of zero.
Now, of course, what will happen even in that direction is: There will be efforts to make sure that the payment system will actually provide a kind of [paperless] service as it is happening, I think, in the case of EgovPay.