As well as running costs you’ve got the filters to replace. Inevitably parts will need replacing too. Presumably, there is a fan in there and something to heat the desiccant? And pump to get the water up from the tank to the dispenser….of course, it still won’t work the way it’s described as it’s silent, so it can’t have a fan to draw the air in. Presumably there will be a HX for hot water that’ll need cleaning and replacing too.