PaterAlf: For people from countries with higher regional pricing than the base price, it would mean that they would get nothing.
Not sure if true.
I recall running the numbers with The Witcher series, and assuming I used the store credit, the whole series was cheaper for me as a European than for an American one, even though the European prices were higher. That may have been a quirk with The Witcher series specifically, but assuming you do use the store credit (and if you own 20% or more of the catalog, you will), then the regional pricing doesn't matter all that much.
Do tell me if you want me to run the numbers again once I'm properly awake.
P.S. There are already times when people get less store credit than others, mainly loyalty sales (see Hard Reset: Redux for example). Some Europeans will get €2.40 in store credit, others will get €0.40. An additional 5% discount would still provide the proper store credit for the price you paid.