The parent isn't saying that there are $500 laptops that are as good as $1k Air. They're saying that there are $500 laptops that are "good enough" for most people's use.

Personally for home use I buy pre-owned Thinkpads and then put Linux on them. They're fine for normal use - Internet, Email and light to moderate SW Development. The screens are mediocre, but I pay £300-£400 (UK). Oh and I don't care about battery age because replacements are inexpensive and require sliding one catch to make the replacement.

Yes, for work I want something more performant and I'm considering pushing work to get me a Macbook (instead of the high-spec Thinkpad I currently have), but that's a different use case.