In the end, both systems are quite similar in terms of acquisition cost
Of course, you can put a positive spin on it. But that doesn’t change what has already been described and reported many times here and elsewhere. A gas boiler with everything included. That means the device, storage tank, LAS (not to be confused with a "real chimney"), installation, connection, adjustment, etc., really everything. Except for the gas connection (which varies from community to community), it amounts to about 1/3 of the investment cost of a complete air-to-water heat pump system. And even including the gas connection (if it's available in the street and doesn’t have to be extended 50-100m over open land) and the token solar system, you end up in the range of 1/2 to 2/3.
Of course, if you don’t want/can’t do the work yourself, then different numbers are possible.
The tough part comes later... quite often with the heat pump you have to intervene yourself because standard settings or much too high heating curves are often used, and the builder then has to fiddle with the system in the first and even the second heating season. So it doesn’t end up heating the hair off one’s head.
There are plenty of experiences and reports about this, not only in this forum.
The CO2 tax also changes little to nothing so far (including all stages already decided). A modern system emits around 1.5-2 tons of CO2 per year, which in 2021 corresponds to an additional burden of 50 euros per year and in 2025 about 110 euros more. Granted, it still takes about 10 years of gas consumption to roughly break even compared to the initial investment for an air-to-water heat pump (without subsidies).
Don't get me wrong. Heat pumps are a great thing. Besides three of my gas boilers, I also operate 4 heat pumps (and two more await installation), but a lot has to come together with a heat pump for the calculation to work out.