The Air will be more expensive than the 18, yes . . . just like the current Air is more expensive than the 17. I have no issues with this because I also have the 17 Pro to use if I need better iPhone cameras and if I require a better camera setup than what my iPhones can provide I have my Nikon D850 camera kit to use for better professional quality pictures.
Personally, the camera on iPhones don't matter much to me as I already have a means to take better quality pictures. I use my iPhone cameras, no matter the model, as a "point and shoot" camera of opportunity. Nothing more for my requirements.
Since launch day, I have enjoyed using my Air because of the added RAM and Pro level processor as well as it's very thin and light profile. I have not experienced any battery anxiety that some users have posted. Not an issue for me as I am always around a charging source and not too concerned with "having to plug in" my Air to recharge it. I just get on with my day and if I have to use a battery pack, it's not the end of the world for me as it seems to be for others.
Like the 13 mini, I have been enjoying using my Air for what it is . . . an exceptionally well engineered iPhone. That's my take on things.
I stopped using "contracts" to get new iPhones going forward. I pay outright for all my devices and am done not having to pay out monthly payments so I have the luxury of choosing which devices I would like to add to my iPhone collection while using them for a little bit.