Hello "Willem81".
There are actually many uncertainties when it comes to the topic of "Sichtestriche" (sometimes also called unique floors). Even among evaluations by colleagues in my department.
The so-called Sichtestriche are directly used (meaning: without floor covering) screeds, which initially place high demands on optical properties. The range goes from high-priced, multiple times ground, partially embedded with glass shards or metal pieces and also colored screeds at around 350,--€/m² over terrazzo screeds at 120,--€/m² up to decorative screed mass, which is available for about 65,--€/m². The simplest solution, a concrete paint for 3.50€/m² on a cement screed ≥ CT-C35, I don’t even want to address here!
So there is a huge spectrum of possibilities with a price range that you rightly wonder about, since you didn’t know the backgrounds before.
I strongly advise against the possibility of producing this surface (except for the concrete paint) as a DIY job!! I have had to evaluate enough areas created by professional companies.
Experiences from practice, which years ago led to one of my published technical articles titled "Wie viel Unikat verträgt der Bauherr?".
It is difficult to manufacture a unique floor when at the same time placing value on an appealing appearance.
-----------------
Regards: KlaRa