So the larger sellers, the ones with turnovers of  $300,000 plus per year, are collecting and sending off their GST as they should? Do you mind if I say 'RUBBISH'.

Ebay sends the sales figures of sellers to the ATO each year.

Will all the cross matching the ATO can do with bank accounts etc these days there would be very few eBay sellers avoiding paying GST if their turnover (including postage) was over the $75,000 mark.