Property purchased 05/22, can we withdraw from the purchase?

No, no obligation to build with him, only the requirement from the city within 3 years after development. So without the consent of the developer, who will most likely refuse, there is no cheap option. Then the option is basically off the table

Just a year ago, the seller would have been pleased, since for every person giving back there was a rich selection of successors who would have immediately paid him about twenty percent more. But that wind has changed, and since the reasons for withdrawal lie entirely on your side, he has no reason to be lenient. But that’s not bad for you, that this withdrawal would be economically unattractive. That way, your anxiety won’t get in your way.

Yes, precisely because of your articles and comments here in the forum, I started reconsidering again; before that, the variant with architect and general contractor was actually the clear favorite

I’m glad. So I’m not such a forum troublemaker after all, as lets "hint at" in his ingratitude speech today ;-) Under which circumstances and following which procedure an architect and then a general contractor can be a good way would certainly be beyond the scope here. The most frequent royal road from my point of view (architect with bidding to which GCs may also gladly participate, and construction management then with the same architect who was already the planner) is still no universal tool or all-purpose solution. It’s different in every single case, but still quickly recognizable with experience. And I’m no Miraculix, you’ll get your magic potion recipe printed out ;-) Afterwards you will be amazed how easy it was (maybe you still know the commercial with Boris for AOL).

but ultimately bought the 470m² plot for €320,000 (including development costs at a fixed price, so a whopping €680/m²).

I also come from the area and know that the Vorderpfalz is expensive building land. But this almost breaks the scale here. €680/m²... crazy. What compromises do you still have to make at that price?

I also come from the area and know that the Vorderpfalz is expensive building land. But this almost breaks the scale here. 680€/sqm... crazy.
What compromises do you still have to make at that price?

I was also surprised. We are building about an hour from Neustadt adW and we have a standard land value of 65€, we even paid less for the developed plot.
I had to google first if that could be true and was shocked how expensive the area is. Although the reference values I found were rather around 550, so I find 680€/sqm quite steep.
The district heating obligation would be a sticking point for me, but I don’t have much knowledge about it.

Shall we just write to an architect and hope that he does the right thing?

The first lesson in building a house is that you only get things started by phone. So call and just make a sales appointment.

I also come from the area and know that the Vorderpfalz is expensive building land. But this almost blows the roof off. €680/sqm... insane.
What compromises do you still have to make at that price?

Yes, a few km further east (towards the forest) and you get twice the plot for less than half the price. In Hassloch, we were offered a plot in a new development area for €600/m² but without, at that time, additional development costs of €130/m². Apparently, only 9 of 30 plots have been sold there so far, so they are probably reconsidering the price. In our area, everything seems to be sold out..

I asked about the plot here:

I was also surprised. We are currently building about an hour from Neustadt adW and we have a standard land value of 65€, we actually paid even less for the developed plot.

I live 30 minutes from NW and the standard land value here is 85EUR.