Hi there,
I was in Japan last week, for a few days. Osaka, Okayama, Imabari. The JYen exchange rate is quite advantageous, but again it depends on what we're talking about.
Unfortunately I cannot recall specific examples such as those you are referring to - Jap designer brands, Bottega V or
Gucci. I do a lot of shopping every time I go to Japan, but this is usually watches, accessories, electronics and some (occasionally) clothing. I have shirts and suits tailor made in either South Korea, Hong Kong or Shanghai so unless it is something very specific then I do my shopping duty free before I fly off my country of residence. This includes bags, shoes or other leather goods.
I do buy a lot of cosmetics, perfumes, etc. and in Osaka (Kansai International Airport - KIX) I have purchased a number of items. Last week I got the lovely Shiso face moisturizer from The Body Shop; this is 'Made in Japan' and I think only available there as yet. There are also Serge Lutens perfumes at KIX but do not remember the prices as I bought one last December.
The accessories available at boutiques are pretty to very good. I got some fantastic Ferragamo cufflinks at their duty free boutique in Narita airport six months back, the Japanese have exquisite taste and only want the best. Therefore there is a lot to find around if you have time for shopping. Regarding bags I believe that it is much better to buy them in places like Hong Kong, but would have to check that one and get back to you.
On the issue of Apple products, I got myself a mini iPad last December - sorry to say I cannot remember how much I paid for it. I got it at the Yodobashi (Akihabara location) store in Tokyo. The iPhone 5 in Japan cannot be sold as standalone device, it is only sold with a mobile telephony contract. For Apple, the best place to get them in Asia is definitely Hong Kong, the prices there are by far the cheapest.
One more thing about Japan: over the years, since 2006 that I've been in the area, I have bought various things there. These range from clothes (e.g. RL underware, RL handerchiefs) to luggage (Nike carry-on golf set) and from watches to electronics. I can ascertain you that their products are top-notch regarding quality. The RL goods I bought were all 'Made in Japan' and their electronics are from the very best batches from any production line, i.e. the Canon dSLR body or lens you will buy in Hong Kong is not the same as those you will buy in Japan. The Japanese have wristwatch models only released in Japan and this is applied in almost every part of the retail industry.