Air-to-air heat pump vs air-to-water heat pump vs ring trench collector - differences

I would have rather estimated it like this (for KfW 55, 185 m² living space) - including ready-to-operate installation -:

1.) Air-to-air heat pump: 20 - 25 TEUR
2.) Air-to-water heat pump including underfloor heating and controlled residential ventilation: 35 to 40 TEUR
3.) Brine-to-water heat pump including underfloor heating and controlled residential ventilation as well as drilling: 45 to 50 TEUR

Then I adjust from drilling to trench collector:

1.) Air-to-air heat pump: 20 - 25 TEUR
2.) Air-to-water heat pump including underfloor heating and controlled residential ventilation: 35 to 40 TEUR
3.) Brine-to-water heat pump including underfloor heating and controlled residential ventilation as well as trench collector: 33-38 TEUR

My subsidy for the collector (I think 4,500€) was about 2,000€ higher than the total costs for the collector including all materials, excavator, excavator operator, etc. (~2,500€). Of course, installation was done in-house, otherwise the price would be relativized. In addition, longer durability of the brine-to-water heat pump, collector lasts anyway 3 lifetimes.

Brutal the increase, these were our prices 2014

If you do it yourself, you can get a trench collector much cheaper... the collector will cost you maybe €2,500 in self-performance (including materials, excavator rental, excavator

My subsidy for the collector (I think €4,500) was about €2,000 higher than the total costs for the collector including all materials, excavator, excavator driver, etc. (~€2,500). Of course, installation by myself.

I don't understand the comparison.

Are you currently comparing a subsidized brine-water heat pump with trench collector to a non-subsidized air-water heat pump?

Currently, there are only percentage-based subsidies. 35% in new construction. This can also be achieved with an air-water heat pump.

The prices I mentioned are without considering any subsidy.