You might try Pak 'n Save, which has a "Costco-like" quality about it, and my wife promises is the best deal for groceries in NZ. Quite literally she is saying to me as I write this "It's a scam, you're paying for it to be nice inside--Pak 'n Save is hori so you're saving money there!"
Her other advice for eating out is to look for takeaways that have specials. We have a Rotorua favorite, Great Spice, which does fantastic Indian food, and on our recent trip they had a Wednesday special, a main with rice and naan bread for $10.99. A great deal--that same food in Germany would certainly be at least 35€. Certainly there similar deals to be found in your area...