Location of city villa or single-family house on 500 m2 plot - rectangular

So this is from the neighbor, so I'm not sure, but mine will be a T 10, probably also from Wienerberger, I think. The Dryfix system, which they now want to use, is apparently also from Wienerberger and certified.

It was the same with us, all good. In a few days it will be warmer again, for your house. Watch how the pallets with a few boards on them serve as scaffolding for masonry, nothing is moved twice.

Photos of the pallets, signs, adhesive buckets, and other labels later help your memory and are taken in front of the eyes of the GU as proof of his honesty (he takes pictures, no false stuff). The question about coffee and sausage at your house can't hurt.

Yeah, had already brought them pretzels and coffee at the foundation slab.

Is it actually so unusual to check invoices that turn out to be significantly higher than expected?
Last week, I received the additional invoice from my general contractor for the earthworks (soil replacement).
It was about 20% higher than expected (1000 EUR). And more than 100% higher than originally quoted. So I naturally wrote that I would like to have it explained.
Beforehand, the offer for soil replacement was made after the geotechnical report when it became clear that more than the 30cm agreed in the construction contract would have to be replaced. At that time, it was still said to be 70cm, so the offer was for 40cm additional to me. During the replacement, I was then called to the construction site because the civil engineer had discovered while digging that it actually had to be 1m. I did a quick calculation in my head, okay, so add another 3/4 - damn. In the end, it was even more. Finally, I was then told that after the demolition, the surrounding terrain at my construction site was about 20cm lower, so they also had to fill up my lot.
Unfortunate, but it happens. It’s not a problem either.
What only surprises me is that it’s then implied and also stated directly that my behavior is somehow not proper.
How do you handle it when something suddenly costs 1000 EUR more than estimated (mind you, we are already talking about additional costs that suddenly just get more expensive)?
Of course, something like that happens more often in house construction, but is it not even allowed to ask why? Should one just nod and smile and even thank when, besides the penultimate shirt, the pants are taken off as well?

Yes, unfortunately it is so, invoices complained about by you and checked and reduced by the [GU] cause teeth grinding at the [GU] and justified suspicion from you of surcharges on further invoices. The [GU] is already eager to build a house for you; if he can charge xx000 € more, he feels better. So, pay if it seems justified. Although more excavation due to the slope angle cannot be calculated proportionally.