If by better you mean cheaper.... then you might be right. Japan is one of the countries where the start of an *A RTW is priced lower than in most other countries. However there are some others, like in Africa, that might also work. It mostly depends on your expenses for positioning yourself and what you will do with the segments at the end of the RTW.

I assume you have found the book-and-fly tool on the *A website where you can easily play with different routes?