Total costs 660 k€ - Please provide assessments

We are also building in BW. Land €380/m², house with 180m², air-water heat pump, on a slope, currently €430,000 = total €610,000. And this is only feasible through a lot of own work and very cheap material costs for sanitary, heating, controlled residential ventilation, and electrical. Therefore, the price is not entirely unrealistic.

Are the 430,000 the pure construction costs and the 610,000 including the land and incidental costs? (Garden?, Kitchen?)

I wonder what’s wrong with my cost plan. Overall, I come up with €50,000 more, but I’m already paying €80,000 less for the land. This certainly won't be saved just by own work and cheap material costs.

I wonder what is going wrong with my cost plan. Overall, I come up with 50,000€ more, but I am already paying 80,000€ less for the plot of land. Surely, this won't be saved just by doing the work yourself and having low material costs.