Turnkey vs. Individual Contracting

On which amount do you actually pay the real estate transfer tax for individual contracts? Only on the shell construction? After all, it is not habitable, on the other hand - how is the tax office supposed to know what I do myself on my house and what is done by a company? Depending on the federal state, with 200k less on the main invoice, there would be up to 13k euros of real estate transfer tax that you do not have to pay.

Purchase of real estate... applies to the purchase price of the property. Unless you buy land and house together from a developer. Then the tax applies to everything.

So either you buy a plot of land without a house, then you pay the real estate transfer tax on the purchase price of the plot. Or you buy a plot of land with a house (existing or from the developer), then the real estate transfer tax is due on the total price.

On which amount does one actually pay the real estate transfer tax for a single award? Only on the shell construction?

I think you are confusing the terms general contractor and property developer here. You do not pay any real estate transfer tax on the refinement of your property.

Unless you buy the land and house together from a developer. Then the tax applies to everything.

Yes, that’s what I meant. Developer-bound plots are not uncommon either.
DOES EVERYTHING mean
1) Tax on (land + shell house) or 2) Tax on (land + shell house + sum of the prices of the individual trades)
?

Yes, that's what I meant. Developer-bound plots are not exactly uncommon.
EVERYTHING means
1) Tax on (plot + shell house) or 2) Tax on (plot + shell house + sum of the prices of the individual trades)
?

I would say: tax on everything you buy from the mentioned developer.
So if you buy plot + shell house from him, then probably that. If you buy plot + turnkey, then on that.
That's how I would interpret it, but I could be wrong.