New semi-detached house - smart home setup with an extra 10,000 EUR?

What would be a typical number of switches for the size of the house?

I am currently planning with 3 in the bedroom (door, nightstands), 1 per children's room, 2 in the living area (scenes + control center), 1 at the entrance (absence), 1 for guests and that’s it. So about 9. However, I already have the goal of this thread (title) in mind: Smart + 10k extra cost. I fear, however, that the 10k won’t be possible.

The classic KNX user does not actually exist, as that would basically contradict what KNX is. It is meant to cover all needs. From the shed to the skyscraper.

I prefer to have one more switch than one too few; the costs only play a minor role when you relate them to the house price?

I know this line of thinking from customers and builders from the first conversations, and most of the time it settles down. It is not really about the costs in your case either. I already wrote that I understood. The money has to come out.

However, this directly contradicts the renunciation of door/window sensors and environmental considerations.

I prefer to have one more switch than one too few

Specifically about this statement:

Also here from experience. Much helps little in this case. Because the traditional way of thinking "a switch on every door frame" simply originated from the constraints of conventional wiring: "somehow you have to be able to switch the light" is neither necessary nor with KNX in the walls classic overengineering. Sure, afterwards you can plaster over the boxes. Smarter is to not have to drill the holes in the first place.

What would be the usual number of switches for the house size?

About one third, maximum half. You simply don’t need more. Despite guests, changing circumstances and/or family growth. Some realize this earlier, others later.

I usually ask why one even has KNX if the installation is operated completely "conventionally," meaning one button for each blind and each light.

Well, the settings can be so different. Our electrician only "knows" and installs Gira. MDT simply does not belong to the established electrical mafia, so they were immediately out for him.

Well, what the GH does not plan for you and where you don't make the most profit, you simply do not "know." MDT in particular is completely broken in terms of price; almost all online retailers are below the regular equity. The electrician just finds that stupid. Understandable, but poor from the customer's perspective.

what’s the point of having KNX if you operate the installation completely "conventionally" anyway,

I ask myself that, and so do new homeowners, again and again. Often it turns out that people simply don’t know any other approach and are completely convinced that it has to be that way. Because you always have to maintain (alleged) full control.

Free paraphrase of the motto: "what the farmer doesn’t know..."

In general, most people are receptive and recognize the potential and possibilities when you show and explain it to them. But there are also the consultation-resistant ones who then get the old familiar in a fancy form for more money. What can you do, the customer is king.

I keep asking myself this, as do the new homeowners. Often it turns out that people simply don't know any other approach and are totally convinced that it has to be that way. Because you always have to keep (the supposed) complete control.

Freely following the motto: "what the farmer doesn’t know…"

Generally, most people are receptive and recognize the potential and possibilities when you show and explain it to them. But there are also those resistant to advice, and they then get the old, familiar stuff in a fancy form for more money. What can you do, the customer is king.

I chose KNX in the first place to be able to move freely among manufacturers in the future and to simplify currently annoying workflows (lower all roller shutters at once, control temperature and ventilation, control outdoor lighting, etc.… there will be more things programmed related to electrical matters!)
A conventional wiring would certainly have been sufficient for the current moment, but having the choice later on to program some scenes was important to me in order to keep walking distances low.
When deciding on KNX or not, costs were the very last thing I considered – these costs are marginal compared to other purchases.
I actually omitted the window contacts because I didn’t see any reason for them; besides, my neighbors are police officers :) , so I thought long and hard about a possible alarm system, too.
The weather station is debatable, but here as well I saw no necessity. We will probably include it later.

Regarding the switches: There are not 32 switches in total, but 9 room controllers and 13 switches (single/double), so 22 in total.
Originally there were only 32 switches without room controllers; we converted 10 switches into 9 controllers.
Room controllers:
2 x living room
1 x dining room
1 x kitchen
1 x guest WC
1 x hallway ground floor
1 x children’s room (his)
1 x children’s room (hers)
1 x bedroom/walk-in closet

Switches:
1 x stairs
1 x exit switch (all lights off/all roller shutters down, etc.)
1 x guest room
1 x study
1 x utility room
1 x storage room
1 x garage
1 x attic
1 x hallway beginning upper floor
1 x hallway end upper floor
1 x central upper floor roller shutters down
2 x bedside "panic switches"

to be able to move freely among manufacturers in the future and to simplify current disruptive workflows (lower all roller shutters at once, control temperature and ventilation, control outdoor lighting, etc...

Yes, in this case and with your choice of the KNX protocol as a means to an end, you did everything right. But you are welcome to start a new thread about your electrical work where everyone can join the discussion. Because as you have confirmed, you are far from the topic of this thread.