On average in Luxembourg, a new flat is sold for 6,051 euros/m2, and the price of an old flat is 4,795 euros/m2 (source Statec - June 2017).
If the price difference is on average 26% between new and old, it is explained by many advantages: 5 reasons to buy new

But other criteria also influence property prices.

The larger the area, the lower the prices

Another variable, whether in new or old buildings, is that prices per square metre decrease as the surface area of the property increases.
Thus an old flat of less than 50 m2 costs on average 5,362 euros/m2, while a flat of more than 130 m2 will cost 4,795 euros/m2. And the same trend exists in new buildings.

The further away from the capital, the lower the prices

Property prices also vary according to the location of the flat. Logically, as you move away from Luxembourg City, flat prices fall. The lowest prices are found in the north of the country. For example, a new flat in the canton of Luxembourg sells for 7,546 euros/m2, whereas in the north of the Grand Duchy the same property sells for 4,663 euros/m2.