Window offer evaluation - Is it okay like this?

: How do you come up with a surcharge of 1,200? I think I can’t do math anymore. :-(

2000 gross - 800 gross equals 1200 gross

The window prices look reasonable - without knowing the quality. However, there is always a good way to find out for yourself. 1. Configure a comparable window in various online shops and compare the price, and 2. enquire with another provider.

But now I know why I don’t like [Raffstores] and will never have any. They are twice as expensive as the windows.

Is this intentional, to have only Quadro P instead of Quadro XP and to take insect protection separately?

100% prepayment is incompatible with withholding for the purpose of securing flawless execution.

Just for comparison from an offer we currently have:

Schüco Living 82 MD, triple glazing Ug = 0.6
1000x2200 fixed glazing, foil on both sides = €360

Schüco Thermoslide SI 82 lift-and-slide door
2300 x 2125, foil on both sides = €2700

Installation and the necessary materials are extra.

I also find the blinds ridiculously expensive. For that money, I'd rather get a full-grown tree from the nursery to provide the shade ;-)

Is this intentional, only Quadro P instead of Quadro XP, and taking insect protection separately?

Thanks in advance for your hint.
The insect protection is intended only for the lift-and-slide door.
That means a insect screen is integrated directly into the lift-and-slide door, which is basically foldable and, in case the sliding door is open, is simply pulled sideways across the opening.
Since we have chosen fixed glazing for all windows (except for the lift-and-slide door), we can theoretically take the blinds without insect protection.
But your question is completely justified.

100% prepayment does not go well with retention for ensuring flawless execution.

Yes, I see it exactly the same way.
I will not accept that.
I have never seen that you have to pay 100 percent upfront. And especially not with an amount of this size.
I will ask the window manufacturer how he envisions the security arrangements.