They are trying to establish the new architecture. Also you still need to shell out $2-3k to get something decent and practically start at $1.5k. I wouldn't call that cheap or even cheaper. What is the past difference you see?
They're all using the exact same CPU, in fact you can make the air perform (almost) just as well as the pro/mini by opening it up and adding a thermal pad: https://www.cultofmac.com/759693/thermal-mod-m1-macbook-air/
Honestly 16GB Air is pretty epic for $1200, though you probably want to spend the extra $200 for a storage bump as well. I'm very happy with the performance for dev tasks, and with my (displaylink) dock it runs multiple screens just fine too.