Your usecase sounds very specific - you mean that because you often need to work in three different operating systems, you usually take say 3 laptops with you when travelling?

I can see why that would benefit you of course, but I can't imagine that's a common scenario. Most devs normally just need one laptop, and while I agree that laptops need less space, for users not doing dev work or other stuff it's unusual for a laptop to be worth the money vs a desktop except in very specific scenarios.

I can't say about every region, but certainly in the US, UK and much of Europe laptops are more expensive than PCs (it makes economic sense: laptops require more engineering due to their constricted space, and they always have inferior cooling for that reason as well). On top of that most laptops aren't easy to open up and change, so it's easier to get away with cheap components in some of them.

It's no longer as big a gap as it was, especially at the budget end, but the performance differences between the two still remain.