Dissatisfied with the final construction cleaning - am I being too picky?

Cleaning the windows from inside/outside including frames and blinds is roughly in that price range.

210 gross per person minus travel costs and deductions. Question to the self-employed here: what remains as net?

You get what you pay for.

Here is the offer text that reached me:

So it was already advertised as post-construction cleaning.
I think I'll follow your advice, clean up once more and write it off as a learning expense.
It is clearly cleaner than before. But I will have to significantly spoil their rating balance. It’s not worth 5 stars to me, not even 3.

I don't (anymore) know how big your house is, but "clearly cleaner than before" would be enough for me for €420.00. I would either do the fine work myself or have to pay significantly more for it.

Just cleaning the windows from inside/outside including frames and blinds is roughly in that price range.

210 gross per person minus travel and deductions. Question for the self-employed here: what remains net?

You get what you pay for.

I would normally agree with that, but neither the windows nor the frames are properly clean.
They were on-site for 6 hours for €210 per person, which is about €35 per hour. Minus taxes, travel, and a bit of material costs, probably even less, but even €20 per hour still seems quite reasonable for cleaning.
Their hourly calculation is none of my business anyway; I paid a fixed price for a service and in my opinion, the service was poorly delivered. Or rather, that would be my question – is that acceptable as a service, or not? I think the set price doesn’t really matter here.
I posted a job and got a clearly defined offer (final construction cleaning, ready to move in). What price they put on it is no free pass to deliver substandard work.

I said at the beginning that our architect recommends the final construction cleaning. However, she also said that we should look for a company that explicitly advertises this. Apparently, it is a specialization of its own. We haven't collected any offers yet, but have already looked for corresponding companies. I expect at least €1000, more likely more. As for the reviews, 5 stars with 7(!) reviews is not really meaningful in my opinion. 100 reviews. Possibly. More likely many more. Of course, you don't find that regionally. Even our kitchen studio, which has a very good reputation, has only about 20 reviews in 30 years. I have found that reviews are a dangerous field. This is by no means meant as criticism of your approach. Rather, from my side, either check it off or have a professional do it again.

Normally, I would agree with that, but neither the windows nor the frames are properly clean. They were on site for 6 hours at €210 per person, which is €35 per hour. Minus tax, travel, and a bit of material, probably even less, but even €20 per hour is still pretty good for cleaning. Their hourly calculation is none of my business anyway, I paid a fixed price for a service and in my opinion the service was delivered poorly. Or actually that would be my question - is this acceptable as a service, or not? I think the price set does not matter at all. I placed an order and received a clearly defined offer (final cleaning, ready to move in). What they charge as a price is not a free pass to deliver substandard work.

If the set price is not supposed to matter, then I can say that for €20/hour, the basic cleaning for an entire single-family house is acceptable. You will just have to do the rest yourself more thoroughly. How do you want to get the paint off the roller blinds? Did you paint yourselves? But that doesn’t matter either; you would have had to clarify your expectations with the cleaning duo in detail beforehand, because final cleaning, ready to move in, is definitely not a clearly defined offer. A construction description indicating that windows are installed in anthracite is just as clearly detailed.

The kitchen was only allowed to be cleaned inside according to the order, not from the outside. Paint and silicone on tiled walls and the roller blind were not included in the order, only on the floor or it says there in the order only if applicable. It's kind of a matter of interpretation. I just believe that the order was not given clearly enough. I have fallen for something like that before. I had a window cleaner for a while until I realized that the frames and windowsill were totally dirty. When I addressed this with the gentleman, he told me that cleaning the windows was contractually agreed, and the rest was not. Well, to me that was part of it, and for him, it was missing from the order. Since then, I have been very thorough and have my wishes confirmed accordingly.