Received GU offer - Assessment of fair offer?

Yes, that's true.. Just with the SmartHome topic (KNX is a MUST :)) I'm already calculating with 15,000 EUR :/ Electric shutters are at least already included in the price. But the additional costs for sanitary installations will definitely come on top for us as well.. At least for the tiles.

Not just the tiles... believe me :D You will be shocked at what kind of sinks, faucets, etc. are installed as standard and what prices are charged for them by the specialist dealers... CRAZY :D

Smart home topic (KNX is a MUST :)) I already calculate with 15,000 EUR :/

o_O So either you only want the KNX for the 3 blinds or the amount is significantly too low. Depending on complexity (so what should all be linked, what automation and scenes need to be programmed) it is said KNX for a single-family house is around 50k EUR. If you have time and motivation to parameterize and program it yourself, you might save 10-15k EUR. But you have to plan very precisely with the electrician beforehand what he connects where and what you will do afterwards. Keep in mind, electrical laymen are not allowed to touch anything at 230V. This also includes the wiring of the actuators.

o_O So either you want KNX only for the 3 venetian blinds or the amount is significantly too low. Depending on complexity (that is what all should be linked, what automations and scenes need to be programmed) people say KNX for a single-family house is around 50K€. If you have the time and desire to parameterize and program it yourself, you can possibly save 10-15K€. But you have to plan very precisely with the electrician beforehand what he connects where and what you do afterwards. Keep in mind, laypersons are not allowed to touch anything at 230V. This also includes the wiring of the actuators.

The electrician should really only do the wiring and connect it in the technical room and leave the description there of what is wired where. A friend of mine, who has set it up at his place, will take care of the programming. But I am also curious what the electrician will charge for the wiring... Do you generally have experience with that? Depending on which software is to be used for the smart home, this easily costs around 2,000 EUR.

Not only the tiles... trust me :D You will be shocked at which sinks, fittings, etc. are installed as standard and what prices are charged for them by the specialist dealers... CRAZY :D

I believe you... let's see if it will be a golden toilet bowl or not :D

Do you basically already have experience with that?

Yes, primarily very bad experience with our electrician, who sold KNX but ultimately had no idea about it. After the electrician gave up on the programming, I dealt with it and learned on my own. The ETS 5 and a server (in my case the Gira X1) were then necessary investments (ETS on sale 600€, X1 about 680€). Plus the components incorrectly planned by the electrician, but that’s another story.
If I had to do it again, I would preferably have the electrician only lay all the cables (with exact instructions where KNX lines and where 230V go) and then do the cabinet wiring myself and also procure the KNX devices myself. The problem is, however, that you (at least I) am not allowed to do the 230V wiring yourself. That means connecting the blinds/shutters, lamps, sockets to the KNX actuator yourself is not allowed for an electrical layman.
Currently, I have a renovation running that is intended to be rented out later. I’m also considering whether to install KNX there – now that I can at least do the parameterizing & programming myself. But in that house, there isn’t much electrical besides lamps and sockets. KNX is somehow exaggerated there anyway, and you definitely won’t get that back in the rent.

10-15k additional cost for KNX is far too little. That barely covers the extra cost for the control cabinet. But then all kinds of sensors and buttons are still missing. And of course the complete programming. In addition, with KNX often significantly more wiring is done because with the possibilities the personal standards increase. TV sockets could be spared in times of Zattoo. 5 network sockets, on the other hand, are really meager.