Even I have trouble motivating the investment in a ground source pump in a really cold climate in Sweden. My regular air-water pump is around £4-7k and has a thermal efficiency (COP) of over 4 (so 1kw electricity is more than 4kw heat) and that’s with no digging or expensive installation.

I get that there is no way Central Europe will switch to ground source, but regular heat pumps should be cheap enough to subsidize.