Just want to disagree with that. "Larger notebook has more power" has been Apple's price discrimination strategy since, oh, the launch of the white iBook. There were occasional exceptions (e.g. the late-2013 15.4" retina MBP with 8 gigs of RAM and no discrete GPU was a relatively modest price bump over the 13"), but in Apple land, if you want a big screen, you were buying a big processor, big GPU, often big storage, etc. It's worth noting that Apple has used the same strategy with the iPad too - if you want a big screen, you're paying BIG BUCKS for a 12.9" iPad Pro.
In Windowsland, it has often been the opposite: there have been a lot of cheap, bulky laptops, 15" or 17" with lower-end internals. And they sell, though maybe not as much as a decade ago - certainly the 17" size is not as common as it was. And the priciest Windows consumer laptops, at least on the non-gaming side, tend to be the super-small/slim Mac imitators like Dell's XPS 13.
Often, frankly, the market is people who don't really take their laptops anywhere, don't care about portability, but for whatever reason don't want a desktop (e.g. the perception that desktops are "messy" with all their cables, take up a lot more desk space, etc). They don't do anything particularly demanding, but they'd like a large screen, possibly not even that high resolution, just because.