Earlier quoted context omitted.
Thwy accept German EC cards, which is an entirely seperate network from MasterCard and Visa (and it's the E in EMV). Mostly because their fees are even 10 times lower than MasterCard's debit card fees.
The "E" in EMV is for Eurocard which is something different (and now merged with MasterCard). The fees for the German Girocard system (which is what colloquially is still called EC) are lower than MasterCard's fees but not by that much anymore nowadays. MasterCard debit should not be 50% more expensive than Girocard considering all fees (which of course still is more) if you shop around a bit. Even Aldi takes them no…
Well, Aldi only takes some type of MasterCard debit - only the Chip + PIN edition Maestro cards, not any of the actual MasterCard network, nor mixed credit/debit cards.