At least in the USA, Sony laptops aren’t really a mainstream device. They’re kind of on the “luxury” end of things, whether deserved or not. Sony is a Japanese company so I wouldn’t have been certain it’s the same there, but if they’re all stupid expensive, that might be why?
Does Dell sell to Japan? They have an outlet store where they sell returns and refurbs for massive discounts, but with the full warranty. You can’t customize it to a tee, but hey, whatever. I’m sure there are other companies that do similar, but Dell is the one I’m familiar with and who I’ve seen with the most selection in that manner. So try looking for direct-from-manufacturer refurb outlets, is what I am saying I guess.
Edit: If you’re looking for actual “Buy this model” advice, that sort of thing is kind of irrelevant for mid-range home computers to be honest. Stock cycles so quickly, it’s more a matter of knowing what your minimum requirements on hardware are, and which brand you’re most comfortable with. Personally, I’ve found HP is some hot crapola and steer far clear of them.