However heat pumps just don’t seem to make any sense, and the more marketing materials I read critically, the less convinced I am of their practicality, nor the integrity of the vendors - if they work similarly to air conditioning units or refrigerators why do they cost 20x as much as those devices?
A refrigerator cools a fairly small volume with excellent insulation, which allows it to use a fairly small compressor running at a single speed. This is cheap.
The big differences between typical air conditioning units and heat pumps are:
they’re set up to move heat both ways (eg: both heating and cooling) which requires a tiny bit of additional hardware
They often have a more substantial compressor to handle the larger temperature difference associated with colder temperatures
They’re a lot more likely to be a system intended to support the whole home instead of a single room
People care about efficiency, which has variable-speed systems getting installed
There’s a lot of demand for them right now, and limited supply