Construction costs are currently skyrocketing

That makes much more sense than a photovoltaic system, because the hot water can be stored cheaply.

This heat pump+photovoltaic cladding here in the forum is really annoying sometimes.
If you only know a hammer, you see a nail in every problem, right?

support the well enough

save a proper amount of fuel and money.

Wrong again. In summer, there is a gigantic surplus of hot water with solar thermal energy, the storage tank just stands full in the corner. Pressure relief valves open, the system practically produces nothing anymore because there is no consumer. 300-1000l storage tanks just stand there uselessly, no one needs these amounts of hot water. Advantage of photovoltaics: excess electricity can be fed into the grid for remuneration, the system pays off much faster (or rather achieves ROI during its lifetime). In winter, both variants have few advantages. If solar thermal is supposed to contribute to heating, it becomes significantly more expensive, as it is hydraulically more complex than pure domestic hot water support. Solar thermal existed only in new buildings to make the gas heating system approvable. Hence the two token collectors on many house roofs. Economically, it is nonsense. It only becomes interesting with particularly high hot water demand, e.g. in multi-family houses or if a pool is to be heated. In a normal single-family house, avoid solar thermal as much as possible.

The neighbor paid 15,000 for his 10 kWp system and feeds into the grid in summer for 6 cents/kWh.

Shall I do the math for you?
Per kWp you get about 1000-1100 kWh per year depending on the region and orientation. Self-consumption 3000 kWh at 40c = €1200 -> the system has paid off after 13 years just through self-consumption.
Now the neighbor also gets feed-in tariff on 7000-8000 kWh, that makes another €450 per year. The system then pays off after 10 years. What do you do with the excess hot water in summer? How much do you get paid for that?

roughly estimated, 2,000 kWh