Hi, welcome to the HUBB.
Firstly I think your question is better suited in the 'Route Planning' section mainly because you will get a wider response, and secondly its worth having a look at some threads of people who have done similar trips.
For what it is worth, here are my thoughts.
If you're wild camping you only have to calculate the cost of fuel and food in the various countries. I dare say that you will not have a problem taking your bike through the Euro countries but you may need to check about carnates with countries such as Iran. In my experience traveling through places like Russia, Kazakhstan, Uzbekistan etc, you only need to declare that you will take the bike with you when you leave and pay insurance which is between $30 and $50 US for one month in each country. When you apply for visas in the countries that you are traveling through, they should give you answers to your questions.
In terms of selling your bike in Australia........that may be a little tricky because of import duties and the like. If I can get solid information on this I will let you know.
What sort of bike are you traveling on ???
Goog luck with the planning.......sounds like a great trip.