getting a laptop here would be a bit troublesome. one would be the OS, most are already installed with the OS and mostly Japanese. You can always change it to English OS, but the problem would be the key arrangement. the alphabets is standard but the other special character would be the problem. Believe it would get you irritated
Prices would not differ much actually, if you are opting for a brand new ones. But there are always a rare find somewhere in akihabara if you know where to look.
this is a japanese site, but you can always compare prices here:
www.kakaku.com -> shows where is the cheapest item can be found all over Japan. Some would even deliver it directly to your place , COD.