Photographic equipment can be rather cheap in Japan. However, for such shops, you need to google surf their site, know exactly what you want, get in and purchase the items straight away. Some can be cheaper by a few hundred bucks if you compare with prices quote in Singapore.
If you want to take a trip to Tokyo, try out those free 2D1N Cathay Pacific stop overs in Hong Kong and shop for your photographic stuff there instead. Tokyo prices are relatively expensive, and prices in Japan on a whole can vary by a large margin. There are some things that are cheaper, but I was not able to find it in the major photography supermarkets i.e. Minolta Scan Dual IV can go for as low as SGD480 in Tokyo.