Many expats report groceries to be very expensive in Luxembourg. Housing prices are also high, though living outside the city is more affordable. Private schools are very expensive, adding to the cost of having a family.
Iceland is expensive relative to much of the world. A few years ago Reykjavik was one of the most expensive cities in the world. The cheapest apartments you’ll find in Reykjavík cost around 10-15 million ISK. You have plenty of choices for 20. Outside Reykjavík prices are considerably lower. For the price of a super cheap Reykjavík apartment you could get a nice house in a more remote area.