Exiting Japan for a Work Visa
 

As I understand, if you are in Japan and you obtain work, you will need to leave Japan to obtain work visa. Does anyone have some idea of costs of the flight for an Australian citizen to go a third country (which is got to be cheaper than Australia) for this purpose?

You can go to Korea for a less than 30,000 yen.

It depends on how long it will take to process the work visa. If you are on a 90 day tourist visa, and it takes more than a month for you to get hired and sponsored, the tourist visa may expire before the work visa is completed. If this is the case, then you'll have to leave the country and return.

They usually stamp you passport when you apply so the 90 days can be extended while the application is processed.

As of several years ago, it is usually not necessary for most nationalities to leave Japan in order to change to a working visa. Check this with immigration before you book a ticket; don't just assume that you have to leave. I know a number of people who have had the change of status processed without leaving Japan.