I have given very detailed explanations on how to legally avoid registering for GST with ebay sales well over $75,000 on the tax thread on Australia seller release 14.1 forum. I wont repeat it all here as it is spaced over several posts that took quite awhile to write. I have used this strategy myself under the guidance of  my accountant and have lodged annual returns with the ATO under this system without problems.  I,m happy to assist with advice if anyone wishes to use the system.