Costs depend on companies, be careful of companies that give you quotes like "from 99$". You usually end up paying a lot more, i know i was burned my first time round. You may be entitled to claim tax back, however you need to be careful, if you apply for tax back and you have not been in the country for 6 months, or have had even a short holiday to fiji for a week, meaning you have never done a 6 month block without leaving oz, you wont be entitled to tax back and can even be fined if you lodge with the ATO!