Construction costs are currently skyrocketing

Yes, you will need more equity. In my opinion, that's not a bad thing. The "oh, the municipality has a new building area, let's just apply spontaneously" is over. More supply for those who have been consistently saving for years with the goal of building/buying a house and not starting with 30k "equity". Everything is normalizing a bit again.

Here in the area (Munich commuter belt) there are places where you aren’t even allowed to apply for a building area if you have more than 150k equity. And preferably at least three children and active in five clubs. The plots, however, sometimes cost 400-500k. Luckily, we didn’t have this equity regulation. But I'm really curious whether they will now loosen these allocation guidelines, because otherwise it really only works if both parents work full-time (with a very good income) and the children spend the whole day in daycare.

Here is another example from practice that I have been observing more and more:

I am in the group "beim blauen f" of Town & Country and have been closely following the posts there for the last two years. We earn quite well and have kept the finances very disciplined during the house construction. In other words: mostly kept things standard and chose very nice tiles for us without extra cost. In addition, complete self-performance on floors and walls.

We always had to rub our eyes in astonishment when the posts and comments repeatedly said, "Which special equipment tiles did you choose? The normal ones are just no good!!", "Who’s 10k sample buffer wasn’t enough either?" "Yes, 20k just for the bathroom and another 8k for electrical!!"

And the nice thing about the blue f: you can see people’s backgrounds quite well through their profiles.

Some have also openly said that they went into follow-up financing for the tiles from Italy.

Situation currently for a few weeks:
The topic of extensive special equipment and upgrades during construction is practically dead. No one asks about that anymore. Everyone is now looking to manage with the affordable financing they secured.

So the effects are also visible very quickly during the construction phase.

If I calculate, the jump from 500,000 € loan amount and 20 years term as a full tiger from 1.1% to the currently usual 3.4% is about +/- 550 € additional costs per month. For 1000 € additional costs, the loan amount must already be close to 900,000 €.

Your numbers are simply wrong. 650,000€ project, 500,000€ loan. The difference between 1.1% and today is exactly the mentioned ~1000€ additional costs per month. Instead of 2300€, it is almost 3300€. Surely everyone can afford that.. Nothing more needs to be said. Except - for 650,000€ you can hardly get existing property + renovation in the metropolitan areas, the prices there are still at 750,000€, 800,000€ and more.

And the nice thing about the blue f: you can see the background people come from quite well through the profiles.

Yes, the nice thing about FB is that you are dealing with people there and not with users who hide behind nicknames. For most, you can infer a lot from the photos.

And even fewer secured 20 years fixed interest at 1%

I count myself among the lucky ones who were able to secure 1.2% for 30 years in December :). Unfortunately, the debt will still be six-figure by the time I retire, but I might sell the house anyway and move to something smaller...

We always had to rub our eyes in disbelief when it was constantly said in the posts and comments, "Which special equipment tiles did you choose? The standard ones are just not acceptable!!", "Who else didn’t have enough with the 10k sampling buffer?" "Yeah, 20k just for the bathroom and another 8k for electrical!!"

Funny, I’m active in 3 Heinz von Heiden forums on the blue F and it’s the same there. Although I notice that hardly anyone builds with a basement anymore. And many build somewhere far out or in the cheaper, economically weaker northern/northeastern federal states.