At Brisbane Airport, the International & Domestic terminals are actually separate, and located almost 3km apart. Given the frequency of the Airtrain schedule, the easiest and fastest way to travel between them is by train. The journey time is only 2 minutes.
For passengers travelling on connecting Virgin Australia flights (meaning both domestic and international travel on Virgin Australia flights), a transfer between terminals is provided at No Charge to you. It must involve flights on the same carrier to/from each terminal. You will need to show us your airline boarding passes when you arrive at either teminal.
If you're travelling with different carriers, the fare is $5.00