Something is different - it's not that one was sold as 'air fryer'.
(I broke my oven door, rather than pay £150 plus labour opted to pay £280 for a new oven. That was a Bosch, certainly not the cheapest possible.)
Assuming you only look at electric fan ovens (the vast vast vast majority these days) more money buys you better insulation mainly. A brand too of course (maybe better R&D/thought gone into the controls/ergonomics etc. hand in hand with that) - but not somehow better food.
'Pro-level' ones obviously cost more, buying reliability & service primarily. Still not somehow better food, don't buy a commercial oven for a home kitchen.
It's largely from disappointment - I assumed initially that they were designed to save oil vs. a deep fryer, that they blasted jets or misted oil over the food. That I think would be novel and interesting.
As it is, if you have an oven already, the RoI is too long to do it on a cost basis. Maybe there's an argument of time-saving as they pre-heat a smaller box quicker? Hardly takes long as it is, I think that's a stretch.
If you don't already have an oven, then yes, if the capacity is not a problem then it's a great option, they start cheaper than bigger ovens... Obviously I suppose.
(I suppose I shouldn't have generalised so much above - I was speaking from my experience in the UK. Other than perhaps a tiny studio flat (single room apartment, no separate bedroom) I would think it's pretty much unheard of to rent somewhere without one here; buying it would normally (almost always) be included, but if not there'd be an obvious gap where yours or your newly purchased one would go.)
There are costs - you waste counterspace and you need to own another thing. But "just buy a convection oven" isn't an option for a lot of people.
Honestly, if they didn't put separate fan temperature/time on the back of stuff (increasingly they don't actually, more and more I'm seeing fan only) I'd honestly never have known anything else existed. I've never lived anywhere with one, didn't see any for sale when I bought one (to replace broken one) a couple of years ago. (UK)
Air fryers should really be called individual ovens. They’re basically the same but more efficient
