Building on a slope with approximately 30 percent incline

Yes, you don't have to level everything flat from one end to the other, as many do. Two levels already help a lot without leveling everything flat. Wood studs/walls/WU concrete are similar in price. The reinforcement costs and possibly the thicker floor slab. In return, you have a retaining wall and one level. The rest can, for example, be left original.

Decisive cost factors besides the house itself are soil class, volume of earthworks, and shoring measures. In addition, where you want vehicles to access, since practical driveways for access from below are also "not without issues" and also take up a lot of land area.
Timber frame construction should only be placed on a stable concrete base. (was our choice).
If you have reserves beyond your budget for unforeseen issues with the earthworks, everything is great. The original budget seems tight. We built a wooden house on a slope and cheerfully - not without the support of the architect - miscalculated. After the civil engineering offer was received, the budget change became clear, and yet there was another deviation because more soil class 7 was found than expected. Without financial flexibility, we would have been under great stress. More details with numbers only via private message.

Were the construction roads able to be built directly up to the house for you? Besides the practical driveway for cars mentioned, these require even higher demands.

My ideas for the "rough/heavy" work would be:
- Tower crane
- Concrete pump
- Walking excavator

As said, all under the premise of leaving the slope as much as possible in its original state.

I have only 120/130 cm height difference from the street to the front door. The main slope comes only behind the house. I estimate that 300-400 sqm will be left to itself. Properly terracing it will cost six figures for something. However, we have laid out 600 sqm relatively flat below. Draw in terrace, pool, utility garden, play area straight away. That adds up to quite a bit.

No, almost 11m height difference, there was already an old path, which we expanded. The construction road later became the driveway. Earthmoving for the construction road approx. 350 m3 and well over 100 tons of natural stone wall made of greywacke blocks for the necessary slope retaining. There was a widening for the crane halfway, which is now a guest or motorhome parking space.

We have very similar conditions, a plot with a south-facing slope, at the street side initially a 2m embankment and then another 5m over 20m width up to the northern building boundary. So a total difference of 7m over 21m, 33%. The plot measures approx. 50x30. Planned is a 2-story single-family house with an attached bungalow for the parents (in other words: a semi-detached house, whereby one half has no roof).

We are still considering, but the plan is as follows:

At the northern boundary is the neighbor’s retaining wall, from there leave 2m space and a small retaining wall of about 1.50m. The slope is to be leveled with 2 terraces at the height of the upper and ground floors, the building will stand on a basement/garage. It is a rocky slope. As far as I understood from your posts, it has to be masonry, so no prefab basement, correct? We would also like to have a partially covered area in front of the garage to have a south terrace on the ground floor (practically above the driveway).

With an 8% incline, I could get the garage to 2.5m height over 30m.

We have no idea yet who we will build with. Due to ancillary costs, perhaps with Danwood, but Wolf Haus and Keitel-Haus are also doing well.

As soon as we know, the surveyor and the soil expert will come. A small piece still belongs to the municipality, which I would like to include for the driveway.

I would be very happy about your opinions, best regards