But even if the median income were €100k, the €400k level was around the cheapest I could find that you could actually live in and wasn't a weekend house, or a reverse-mortgage you'd only get to use when the seller died, or a building opportunity with no land, or they're rented out and as Germany has fantastic protection for tenants you are not going to move in etc.
If the standard is 4 years, even then you'd be excluding 50% of the households from ownership at €100k/year and €400k minimum prices. As is, €43k/year is closer to 9.5 years income still not being enough for 50% of households.