Yeah, recently saw some numbers for air-to-air vs air-to-groundwater, and it break even after more than 25 years, with more than twice the initial cost
Here in Norway you can get a decent air-to-air minisplit installed for $2k. I've not heard of anyone who paid less than 10x that for an air-to-ground or water-to-ground system, drilling 500-1000 feet is expensive.
The well that you drill will last a 100 years if you don't have bad luck. That is half the cost of installation.
The water/water heatpump unit in my house is 20 years old and has not had any major failures yet. I hope it will run for another ten years before the compressor gives up, but it is indeed approaching its calculated technical lifespan. I estimate it will set me back €10k to have it replaced.
Air/air is the cheaper option over time, even in most of Scandinavia with coldish winters. The main drawback of air/air systems are that they are loud and ugly and therefore annoy both yourself and your neighbours.
