Single-family house on a steep slope - Bavaria

One reads a lot of different things on the internet. According to the GU, there is also an official index. Can an average price per sqm be derived from this?

There is also an average shopping basket, based on which the inflation rate is calculated. But this says very little about your personal weekly shopping, as your basket might be different. And even if it were the same, different supermarkets have different prices. On the internet, one reads various things because people have built different things and that at different times and in different regions.