It would cost substantially more for a small-scale company to produce a laptop with the quality of MacBooks than it costs Apple. That cost difference would have to be passed to the consumer.
Additionally, a lot of these niche laptop brands don't even manufacture their own laptops because they're not even at the scale where designing and manufacturing a board and chassis would be financially viable. Many are white-label or ODM laptops. https://en.wikipedia.org/wiki/Original_design_manufacturer